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WHAT CHARACTERS ARE ALLOWED IN AN EMAIL ADDRESS?
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Asked 14 years, 5 months ago
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I'm not asking about full email validation.
I just want to know what are allowed characters in user-name and server parts of
email address. This may be oversimplified, maybe email adresses can take other
forms, but I don't care. I'm asking about only this simple form:
user-name@server (e.g. wild.wezyr@best-server-ever.com) and allowed characters
in both parts.
* forms
* email
* email-validation
* email-address
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edited Mar 19, 2017 at 10:06
kevinarpe
21k2727 gold badges131131 silver badges161161 bronze badges
asked Jan 12, 2010 at 14:13
WildWezyrWildWezyr
10.5k66 gold badges2424 silver badges2828 bronze badges
22
* 270
The + is allowed. It drives me nuts when web sites don't allow it because my
email has a + in it and so many sites don't allow it.
– Dan Herbert
Commented Jan 12, 2010 at 14:16
* 12
Earlier question covering the same material:
stackoverflow.com/questions/760150/. The sad thing is, even though that
question is almost 8 months older than this one, the older question has much
better answers. Almost all the answers below were already out of date when
they were originally posted. See Wikipedia entry (and don't worry, it has
relevant official references).
– John Y
Commented Jul 20, 2012 at 20:56
* 29
Contrary to several answers, spaces are allowed in the local part of email
addresses, if quoted. "hello world"@example.com is valid.
– Quitting Due To Antisemitism
Commented Jul 8, 2014 at 6:34
* 13
@LaraRuffleColes - For Gmail, when you create an email account, it doesn't
allow you to create addresses containing a "+" sign. The "+" sign
("Plus-addressing") allows anyone with a Gmail address to add a "+" sign
followed by a "string" to the end of their username to create an "alternate"
("alias") email address to use for their account. Example:
"example@gmail.com", "example+tag@gmail.com". A typical (and probably
"Primary") use of this is to be able to create alias email addresses for your
account which allow you to tag and filter incoming email messages,
theoretically filtered by sender.
– Kevin Fegan
Commented Sep 26, 2016 at 17:49
* 10
@Andrew The reverse is much more common. If a site can't be trusted to allow
proper email addresses, I don't trust them to handle my personal information.
– Dan Herbert
Commented Apr 6, 2018 at 16:15
| Show 17 more comments
18 ANSWERS 18
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See RFC 5322: Internet Message Format and, to a lesser extent, RFC 5321: Simple
Mail Transfer Protocol.
RFC 822 also covers email addresses, but it deals mostly with its structure:
addr-spec = local-part "@" domain ; global address
local-part = word *("." word) ; uninterpreted
; case-preserved
domain = sub-domain *("." sub-domain)
sub-domain = domain-ref / domain-literal
domain-ref = atom ; symbolic reference
where an atom and word are defined as
; ( Octal, Decimal.)
CHAR = <any ASCII character> ; ( 0-177, 0.-127.)
CTL = <any ASCII control ; ( 0- 37, 0.- 31.)
character and DEL> ; ( 177, 127.)
specials = "(" / ")" / "<" / ">" / "@" ; Must be in quoted-
/ "," / ";" / ":" / "\" / <"> ; string, to use
/ "." / "[" / "]" ; within a word.
atom = 1*<any CHAR except specials, SPACE and CTLs>
word = atom / quoted-string
And as usual, Wikipedia has a decent article on email addresses:
> The local-part of the email address may use any of these ASCII characters:
>
> * uppercase and lowercase Latin letters A to Z and a to z;
> * digits 0 to 9;
> * special characters !#$%&'*+-/=?^_`{|}~;
> * dot ., provided that it is not the first or last character unless quoted,
> and provided also that it does not appear consecutively unless quoted (e.g.
> John..Doe@example.com is not allowed but "John..Doe"@example.com is
> allowed);
> * space and "(),:;<>@[\] characters are allowed with restrictions (they are
> only allowed inside a quoted string, as described in the paragraph below,
> and in addition, a backslash or double-quote must be preceded by a
> backslash);
> * comments are allowed with parentheses at either end of the local-part; e.g.
> john.smith(comment)@example.com and (comment)john.smith@example.com are
> both equivalent to john.smith@example.com.
In addition to ASCII characters, as of 2012 you can use international characters
above U+007F, encoded as UTF-8 as described in the RFC 6532 spec and explained
on Wikipedia. Note that as of 2019, these standards are still marked as
Proposed, but are being rolled out slowly. The changes in this spec essentially
added international characters as valid alphanumeric characters (atext) without
affecting the rules on allowed & restricted special characters like !# and @:.
For validation, see Using a regular expression to validate an email address.
The domain part is defined as follows:
> The Internet standards (Request for Comments) for protocols mandate that
> component hostname labels may contain only the ASCII letters a through z (in a
> case-insensitive manner), the digits 0 through 9, and the hyphen (-). The
> original specification of hostnames in RFC 952, mandated that labels could not
> start with a digit or with a hyphen, and must not end with a hyphen. However,
> a subsequent specification (RFC 1123) permitted hostname labels to start with
> digits. No other symbols, punctuation characters, or blank spaces are
> permitted.
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edited Mar 30 at 8:56
theking2
2,51022 gold badges3333 silver badges4242 bronze badges
answered Jan 12, 2010 at 14:15
Anton GogolevAnton Gogolev
115k3939 gold badges203203 silver badges291291 bronze badges
20
* 25
@WildWzyr, It's not that simple. Email addresses have a lot of rules for what
is allowed. It's simpler to refer to the spec than to list out all of them.
If you want the complete Regex, check here to get an idea of why it's not so
simple: regular-expressions.info/email.html
– Dan Herbert
Commented Jan 12, 2010 at 14:20
* 6
there is no simple list, just because you want something simple doesn't mean
it will be so. some characters can only be in certain locations and not in
others. you can't have what you want all the time.
– user177800
Commented Jan 12, 2010 at 14:28
* 16
@WildWezyr Well, the full-stop character is allowed in the local-part. But
not at the start or end. Or with another full-stop. So the answer IS NOT as
simple as just a list of allowed characters, there are rules as to how those
characters may be used - .ann..other.@example.com is not a valid email
address, but ann.other@example.com is, even though both use the same
characters.
– Mark Pim
Commented Jan 12, 2010 at 14:30
* 14
Also, remember that with internationalized domain names coming in, the list
of allowed characters will explode.
– Chinmay Kanchi
Commented Jan 12, 2010 at 15:18
* 55
This is no longer the valid answer, due to internationalized addresses. See
Mason's answer.
– ZacharyP
Commented Dec 6, 2011 at 17:59
| Show 15 more comments
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Watch out! There is a bunch of knowledge rot in this thread (stuff that used to
be true and now isn't).
To avoid false-positive rejections of actual email addresses in the current and
future world, and from anywhere in the world, you need to know at least the
high-level concept of RFC 3490, "Internationalizing Domain Names in Applications
(IDNA)". I know folks in US and A often aren't up on this, but it's already in
widespread and rapidly increasing use around the world (mainly the non-English
dominated parts).
The gist is that you can now use addresses like mason@日本.com and
wildwezyr@fahrvergnügen.net. No, this isn't yet compatible with everything out
there (as many have lamented above, even simple qmail-style +ident addresses are
often wrongly rejected). But there is an RFC, there's a spec, it's now backed by
the IETF and ICANN, and--more importantly--there's a large and growing number of
implementations supporting this improvement that are currently in service.
I didn't know much about this development myself until I moved back to Japan and
started seeing email addresses like hei@やる.ca and Amazon URLs like this:
http://www.amazon.co.jp/エレクトロニクス-デジタルカメラ-ポータブルオーディオ/b/ref=topnav_storetab_e?ie=UTF8&node=3210981
I know you don't want links to specs, but if you rely solely on the outdated
knowledge of hackers on Internet forums, your email validator will end up
rejecting email addresses that non-English-speaking users increasingly expect to
work. For those users, such validation will be just as annoying as the
commonplace brain-dead form that we all hate, the one that can't handle a + or a
three-part domain name or whatever.
So I'm not saying it's not a hassle, but the full list of characters "allowed
under some/any/none conditions" is (nearly) all characters in all languages. If
you want to "accept all valid email addresses (and many invalid too)" then you
have to take IDN into account, which basically makes a character-based approach
useless (sorry), unless you first convert the internationalized email addresses
(dead since September 2015, used to be like this—a working alternative is here)
to Punycode.
After doing that you can follow (most of) the advice above.
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edited Oct 21, 2020 at 9:03
David Veszelovszki
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answered Jan 15, 2010 at 12:01
MasonMason
5,21144 gold badges2626 silver badges2424 bronze badges
9
* 20
Right; behind the scenes, the domain names are still just ASCII. But, if your
web app or form accepts user-entered input, then it needs to perform the same
job that the web browser or mail client does when the user inputs an IDN
hostname: to convert the user input into DNS-compatible form. Then validate.
Otherwise, these internationalized email addresses will not pass your
validation. (Converters like the one I linked to only modify the non-ASCII
characters they are given, so it is safe to use them on non-internationalized
email addresses (those are just returned unmodified).)
– Mason
Commented Jan 15, 2010 at 13:55
* 3
For Javascript devs, I'm now researching methods of doing this, and
Punycode.js seems to be the most complete and polished solution.
– wwaawaw
Commented Oct 7, 2012 at 7:41
* 5
Note that Internationalized Email (as currently defined) does not convert
non-ASCII addresses using punycode or similar, instead extending large
portions of the SMTP protocol itself to use UTF8.
– IMSoP
Commented May 26, 2014 at 21:30
* 4
Am I missing something or does this fail to answer the question? I am reading
'the other answer is wrong, you need to accept more characters' but then
fails to state which extra characters. I also couldn't (easily) see in that
RFC whether it means all Unicode code points or just the BMP.
– Samuel Harmer
Commented Feb 5, 2017 at 18:32
* 3
This seems to be on the right track to being the correct answer. I bet it
would get a lot more votes if you included specifics about reserved and
allowed characters.
– Sean
Commented Mar 17, 2017 at 18:20
| Show 4 more comments
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The format of e-mail address is: local-part@domain-part (max. 64@255 characters,
no more 256 in total).
The local-part and domain-part could have different set of permitted characters,
but that's not all, as there are more rules to it.
In general, the local part can have these ASCII characters:
* lowercase Latin letters: abcdefghijklmnopqrstuvwxyz,
* uppercase Latin letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ,
* digits: 0123456789,
* special characters: !#$%&'*+-/=?^_`{|}~,
* dot: . (not first or last character or repeated unless quoted),
* space punctuations such as: "(),:;<>@[\] (with some restrictions),
* comments: () (are allowed within parentheses, e.g.
(comment)john.smith@example.com).
Domain part:
* lowercase Latin letters: abcdefghijklmnopqrstuvwxyz,
* uppercase Latin letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ,
* digits: 0123456789,
* hyphen: - (not first or last character),
* can contain IP address surrounded by square brackets: jsmith@[192.168.2.1] or
jsmith@[IPv6:2001:db8::1].
These e-mail addresses are valid:
* prettyandsimple@example.com
* very.common@example.com
* disposable.style.email.with+symbol@example.com
* other.email-with-dash@example.com
* x@example.com (one-letter local part)
* "much.more unusual"@example.com
* "very.unusual.@.unusual.com"@example.com
* "very.(),:;<>[]\".VERY.\"very@\ \"very\".unusual"@strange.example.com
* example-indeed@strange-example.com
* admin@mailserver1 (local domain name with no top-level domain)
* #!$%&'*+-/=?^_`{}|~@example.org
* "()<>[]:,;@\\"!#$%&'-/=?^_`{}| ~.a"@example.org
* " "@example.org (space between the quotes)
* example@localhost (sent from localhost)
* example@s.solutions (see the List of Internet top-level domains)
* user@com
* user@localserver
* user@[IPv6:2001:db8::1]
And these examples of invalid:
* Abc.example.com (no @ character)
* A@b@c@example.com (only one @ is allowed outside quotation marks)
* a"b(c)d,e:f;gi[j\k]l@example.com (none of the special characters in this
local part are allowed outside quotation marks)
* just"not"right@example.com (quoted strings must be dot separated or the only
element making up the local part)
* this is"not\allowed@example.com (spaces, quotes, and backslashes may only
exist when within quoted strings and preceded by a backslash)
* this\ still\"not\allowed@example.com (even if escaped (preceded by a
backslash), spaces, quotes, and backslashes must still be contained by
quotes)
* john..doe@example.com (double dot before @); (with caveat: Gmail lets this
through)
* john.doe@example..com (double dot after @)
* a valid address with a leading space
* a valid address with a trailing space
Source: Email address at Wikipedia
--------------------------------------------------------------------------------
Perl's RFC2822 regex for validating emails:
(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:
\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(
?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[
\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\0
31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\
](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+
(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:
(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)
?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\
r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[
\t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)
?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t]
)*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[
\t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*
)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)
*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+
|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r
\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:
\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t
]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031
]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](
?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?
:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?
:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?
:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?
[ \t]))*"(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\]
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|
\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>
@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"
(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?
:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[
\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-
\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(
?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;
:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([
^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\"
.\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\
]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\
[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\
r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\]
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]
|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \0
00-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\
.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,
;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|"(?
:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[
^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\]
]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*(
?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(
?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[
\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t
])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t
])+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?
:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|
\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:
[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".\[\
]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)
?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["
()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)
?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>
@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[
\t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,
;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?
(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\\".
\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:
\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[
"()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])
*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])
+|\Z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\
.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(
?:\r\n)?[ \t])*))*)?;\s*)
> The full regexp for RFC2822 addresses was a mere 3.7k.
See also: RFC 822 Email Address Parser in PHP.
--------------------------------------------------------------------------------
The formal definitions of e-mail addresses are in:
* RFC 5322 (sections 3.2.3 and 3.4.1, obsoletes RFC 2822), RFC 5321, RFC 3696,
* RFC 6531 (permitted characters).
--------------------------------------------------------------------------------
Related:
* The true power of regular expressions
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edited May 23, 2018 at 11:47
answered Aug 5, 2016 at 10:45
kenorbkenorb
162k9393 gold badges697697 silver badges761761 bronze badges
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* 23
As an extra caution to would-be implementers of this regex: Don't. Just
verify that it folows the format something@something.something and call it a
day.
– Chris Sobolewski
Commented Sep 7, 2017 at 14:41
* 1
While something like this is not maintainable, it is a nice exercise to
decode and actually figure out what it does
– unjankify
Commented Feb 27, 2018 at 16:53
* 9
Madness I say. Who would ever use it in production. There is a point where
regular expression should no longer be used. It is far beyond that point.
– tomuxmon
Commented Jun 14, 2019 at 7:18
* 3
Something I see a lot is "validate according to RFC822". This isn't actually
what's usually needed. RFC822 doesn't define addresses that can be sent to;
it defines addresses that can appear in messages, which is not the same
thing. Addresses that can be sent to is determined in RFC821 (SMTP) and
follow-on standards. In particular this spec does not allow comments,
excluding addresses like a@abc(bananas)def.com that are valid RFC822
addresses but can't be sent to. For this reason, many email validators are
validating against the wrong thing.
– Synchro
Commented Sep 18, 2020 at 9:02
* 2
@ChrisSobolewski absolutely. The aim of this verification is to help the
user, and avoid obvious mistakes (such as forgetting @ or similar). A split
on the email against @ and checking if it returns two non zero strings is
enough.
– WoJ
Commented Sep 8, 2023 at 10:00
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Wikipedia has a good article on this, and the official spec is here. From
Wikipdia:
> The local-part of the e-mail address may use any of these ASCII characters:
>
> * Uppercase and lowercase English letters (a-z, A-Z)
> * Digits 0 to 9
> * Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~
> * Character . (dot, period, full stop) provided that it is not the first or
> last character, and provided also that it does not appear two or more times
> consecutively.
>
> Additionally, quoted-strings (ie: "John Doe"@example.com) are permitted, thus
> allowing characters that would otherwise be prohibited, however they do not
> appear in common practice. RFC 5321 also warns that "a host that expects to
> receive mail SHOULD avoid defining mailboxes where the Local-part requires (or
> uses) the Quoted-string form".
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edited Oct 7, 2021 at 5:46
CommunityBot
111 silver badge
answered Jan 12, 2010 at 14:20
Mike WellerMike Weller
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2
* @WildWezyr Valid hostnames, which could be an ip address, FQN, or something
resolvable to an local network host.
– JensenDied
Commented Jan 12, 2010 at 14:36
* Quoted strings were essential for passing through a gateway, remember Banyan
Vines?
– mckenzm
Commented Nov 1, 2018 at 3:43
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The accepted answer refers to a Wikipedia article when discussing the valid
local-part of an email address, but Wikipedia is not an authority on this.
IETF RFC 3696 is an authority on this matter, and should be consulted at section
3. Restrictions on email addresses on page 5:
> Contemporary email addresses consist of a "local part" separated from a
> "domain part" (a fully-qualified domain name) by an at-sign ("@"). The syntax
> of the domain part corresponds to that in the previous section. The concerns
> identified in that section about filtering and lists of names apply to the
> domain names used in an email context as well. The domain name can also be
> replaced by an IP address in square brackets, but that form is strongly
> discouraged except for testing and troubleshooting purposes.
>
> The local part may appear using the quoting conventions described below. The
> quoted forms are rarely used in practice, but are required for some legitimate
> purposes. Hence, they should not be rejected in filtering routines but, should
> instead be passed to the email system for evaluation by the destination host.
>
> The exact rule is that any ASCII character, including control characters, may
> appear quoted, or in a quoted string. When quoting is needed, the backslash
> character is used to quote the following character. For example
>
> Abc\@def@example.com
>
>
> is a valid form of an email address. Blank spaces may also appear, as in
>
> Fred\ Bloggs@example.com
>
>
> The backslash character may also be used to quote itself, e.g.,
>
> Joe.\\Blow@example.com
>
>
> In addition to quoting using the backslash character, conventional
> double-quote characters may be used to surround strings. For example
>
> "Abc@def"@example.com
>
> "Fred Bloggs"@example.com
>
>
> are alternate forms of the first two examples above. These quoted forms are
> rarely recommended, and are uncommon in practice, but, as discussed above,
> must be supported by applications that are processing email addresses. In
> particular, the quoted forms often appear in the context of addresses
> associated with transitions from other systems and contexts; those
> transitional requirements do still arise and, since a system that accepts a
> user-provided email address cannot "know" whether that address is associated
> with a legacy system, the address forms must be accepted and passed into the
> email environment.
>
> Without quotes, local-parts may consist of any combination of alphabetic
> characters, digits, or any of the special characters
>
> ! # $ % & ' * + - / = ? ^ _ ` . { | } ~
>
>
> period (".") may also appear, but may not be used to start or end the local
> part, nor may two or more consecutive periods appear. Stated differently, any
> ASCII graphic (printing) character other than the at-sign ("@"), backslash,
> double quote, comma, or square brackets may appear without quoting. If any of
> that list of excluded characters are to appear, they must be quoted. Forms
> such as
>
> user+mailbox@example.com
>
> customer/department=shipping@example.com
>
> $A12345@example.com
>
> !def!xyz%abc@example.com
>
> _somename@example.com
>
>
> are valid and are seen fairly regularly, but any of the characters listed
> above are permitted.
As others have done, I submit a regex that works for both PHP and JavaScript to
validate email addresses:
/^[a-z0-9!'#$%&*+\/=?^_`{|}~-]+(?:\.[a-z0-9!'#$%&*+\/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-zA-Z]{2,}$/i
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edited Apr 2, 2022 at 16:04
answered Dec 4, 2015 at 20:35
MacMac
1,5262222 silver badges2828 bronze badges
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* 1
Technically e-mail addresses are allowed also in TLD, so you may consider
changing last group's + to *. OTOH, technically valid address in TLD may be a
blank typo, as these addresses are far less common. Spec vs. life… ;-)
– Cromax
Commented Mar 7, 2023 at 17:06
* @Cromax - exactly. There has to be a happy medium between what we CAN do vs.
what is USUALLY done.
– Mac
Commented Mar 10, 2023 at 22:40
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You can start from wikipedia article:
* Uppercase and lowercase English letters (a-z, A-Z)
* Digits 0 to 9
* Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~
* Character . (dot, period, full stop) provided that it is not the first or
last character, and provided also that it does not appear two or more times
consecutively.
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answered Jan 12, 2010 at 14:20
VladimirVladimir
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Google do an interesting thing with their gmail.com addresses. gmail.com
addresses allow only letters (a-z), numbers, and periods(which are ignored).
e.g., pikachu@gmail.com is the same as pi.kachu@gmail.com, and both email
addresses will be sent to the same mailbox. PIKACHU@gmail.com is also delivered
to the same mailbox.
So to answer the question, sometimes it depends on the implementer on how much
of the RFC standards they want to follow. Google's gmail.com address style is
compatible with the standards. They do it that way to avoid confusion where
different people would take similar email addresses e.g.
*** gmail.com accepting rules ***
d.oy.smith@gmail.com (accepted)
d_oy_smith@gmail.com (bounce and account can never be created)
doysmith@gmail.com (accepted)
D.Oy'Smith@gmail.com (bounce and account can never be created)
The wikipedia link is a good reference on what email addresses generally allow.
http://en.wikipedia.org/wiki/Email_address
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edited Mar 21, 2014 at 12:01
gaoithe
4,31833 gold badges3232 silver badges3939 bronze badges
answered Jan 18, 2012 at 9:34
Angel KohAngel Koh
13.1k77 gold badges6868 silver badges9494 bronze badges
5
* 3
Yea this is a great answer about why Gmail does not allow to CREATE emails
with this. But you can send and recieve emails from {john'doe}@my.server with
no problem. Tested with hMail server too.
– Piotr Kula
Commented Jul 15, 2014 at 14:25
* You can test your client by sending an email to {piotr'kula}@kula.solutions -
If it works you will get a nice auto reply form it. Otherwise nothing will
happen.
– Piotr Kula
Commented Jul 15, 2014 at 14:29
* 3
Gmail does follow RFC 6530 in the sense that every possible e-mail address
allowed by Gmail is valid according to the RFC. Gmail just chooses to further
restrict the set of allowable addresses with additional rules, and to make
otherwise similar addresses with dots in the local part, optionally followed
by "+" and alphanumeric characters, synonymous.
– Teemu Leisti
Commented Jan 20, 2015 at 13:03
* Google limits the account creation criteria... I imagine they scrub the
incoming email account string of the extra "punctuation" and trailing plus
prepended alias string sign so that the mail can be routed to the proper
account. Easy peasy. In doing so, they effectively don't allow people to
create just-bein-a-jerk email addresses so that valid addresses created will
often pass simple and most complex validations.
– BradChesney79
Commented Feb 8, 2018 at 20:41
* It's not just gmail, Some providers have "relaying filters" that reject
certain quoted strings, particularly containing "=" as if they were
delimiters. This is to block users from setting up gateways and nesting spam
addresses in the private quoted string. "@" is valid but "=@=" is not
(considered) valid.
– mckenzm
Commented Dec 6, 2018 at 2:21
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Check for @ and . and then send an email for them to verify.
I still can't use my .name email address on 20% of the sites on the internet
because someone screwed up their email validation, or because it predates the
new addresses being valid.
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answered Jun 11, 2013 at 19:28
Richard MaxwellRichard Maxwell
51855 silver badges77 bronze badges
2
* 9
Even . isn't strictly necessary; I've heard of at least one case of an email
address at a top level domain (specifically ua). The address was <name>@ua --
no dot!
– user1311045
Commented Nov 28, 2013 at 1:37
* This is pretty much the easiest way not to mess up your validation, because
almost everything is allowed, and if something isn't allowed, the recipient's
server will let you know.
– Avamander
Commented Jan 13, 2018 at 11:16
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The short answer is that there are 2 answers. There is one standard for what you
should do. ie behaviour that is wise and will keep you out of trouble. There is
another (much broader) standard for the behaviour you should accept without
making trouble. This duality works for sending and accepting email but has broad
application in life.
For a good guide to the addresses you create; see:
https://www.jochentopf.com/email/chars.html
To filter valid emails, just pass on anything comprehensible enough to see a
next step. Or start reading a bunch of RFCs, caution, here be dragons.
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edited Jun 23, 2021 at 8:50
ygoe
19.6k2525 gold badges119119 silver badges227227 bronze badges
answered Mar 1, 2012 at 1:50
Michael JAMESMichael JAMES
9711 silver badge11 bronze badge
3
* 1
The link is gone. What content was there?
– ygoe
Commented May 26, 2019 at 13:49
* @ygoe yeah site is down, Here is the archive version from ~2012 :
web.archive.org/web/20120807105804/https://www.remote.org/…
– MilMike
Commented Jun 18, 2021 at 11:11
* @MilMike Thank you, from there I found the new URL of that page and edited
the answer.
– ygoe
Commented Jun 23, 2021 at 8:50
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Name:
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!#$%&'*+-/=?^_`{|}~.
Server:
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-.
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edited Jul 27, 2012 at 17:34
answered Jan 18, 2012 at 9:34
ThinkingStiffThinkingStiff
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What about <> and []? E.g. "()<>[]:,;@\\\"!#$%&'-/=?^_{}| ~.a"@example.org`?
– kenorb
Commented Aug 5, 2016 at 10:11
* 24
Please cite sources. Without sources, this looks like conjecture.
– Mathieu K.
Commented Feb 14, 2017 at 17:33
* 17
This is out of date, and possibly was never correct.
– Jason Harrison
Commented Nov 15, 2017 at 17:53
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A lot many have already attempted answering this question. A lot many have also
said that many answers are already outdated. Here is my answer, as things stand
in 2022.
The answer to the question is obviously not as simple as it has been posed. The
proposed standards when it comes to naming of a mailbox name, to be specific,
<user-name> in this context, alongwith the interpretations of those RFCs are far
and many.
For the <user-name> part, Universal Acceptance Steering Group has put up a
detailed guideline as to what all constitute an e-mail ID local part in a
document titled UASG-028 here.
For the <server> part, all the characters mentioned herein "The Unicode Code
Points and Internationalized Domain Names for Applications (IDNA)" with the
character status "PVALID". Also, the characters with status as "CONTEXTJ" and
"CONTEXTO" are valid in certain contexual conditions.
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answered Jul 7, 2022 at 11:50
ThinkTransThinkTrans
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A good read on the matter.
Excerpt:
These are all valid email addresses!
"Abc\@def"@example.com
"Fred Bloggs"@example.com
"Joe\\Blow"@example.com
"Abc@def"@example.com
customer/department=shipping@example.com
\$A12345@example.com
!def!xyz%abc@example.com
_somename@example.com
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edited Aug 6, 2016 at 9:46
Billal Begueradj
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answered Jan 6, 2015 at 16:33
Luke MadhangaLuke Madhanga
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I was wondering about the '@' before the domain part. Can that be used?
– Saiyaff Farouk
Commented Mar 16, 2017 at 12:09
* @SaiyaffFarouk according to the specification, yes. However, most mail
providers likely won't allow it as part of their own validation
– Luke Madhanga
Commented Mar 16, 2017 at 20:04
* that blog lists Joe.\\Blow@example.com without quotes. Is this actually valid
? It doesn't seem clear given the answers here, but I'm asking because I have
seen (very rare) cases of DNS SoA rname email strings that contain
backslashes.
– wesinat0r
Commented Apr 22, 2020 at 15:35
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The answer is (almost) ALL (7-bit ASCII).
If the inclusion rules is "...allowed under some/any/none conditions..."
Just by looking at one of several possible inclusion rules for allowed text in
the "domain text" part in RFC 5322 at the top of page 17 we find:
dtext = %d33-90 / ; Printable US-ASCII
%d94-126 / ; characters not including
obs-dtext ; "[", "]", or "\"
the only three missing chars in this description are used in domain-literal [],
to form a quoted-pair \, and the white space character (%d32). With that the
whole range 32-126 (decimal) is used. A similar requirement appear as "qtext"
and "ctext". Many control characters are also allowed/used. One list of such
control chars appears in page 31 section 4.1 of RFC 5322 as obs-NO-WS-CTL.
obs-NO-WS-CTL = %d1-8 / ; US-ASCII control
%d11 / ; characters that do not
%d12 / ; include the carriage
%d14-31 / ; return, line feed, and
%d127 ; white space characters
All this control characters are allowed as stated at the start of section 3.5:
.... MAY be used, the use of US-ASCII control characters (values
1 through 8, 11, 12, and 14 through 31) is discouraged ....
And such an inclusion rule is therefore "just too wide". Or, in other sense, the
expected rule is "too simplistic".
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edited Oct 7, 2021 at 13:39
CommunityBot
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answered Jun 21, 2015 at 4:56
user2350426user2350426
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As can be found in this Wikipedia link
> The local-part of the email address may use any of these ASCII characters:
>
> * uppercase and lowercase Latin letters A to Z and a to z;
>
> * digits 0 to 9;
>
> * special characters !#$%&'*+-/=?^_`{|}~;
>
> * dot ., provided that it is not the first or last character unless quoted,
> and provided also that it does not appear consecutively unless quoted (e.g.
> John..Doe@example.com is not allowed but "John..Doe"@example.com is
> allowed);
>
> * space and "(),:;<>@[\] characters are allowed with restrictions (they are
> only allowed inside a quoted string, as described in the paragraph below,
> and in addition, a backslash or double-quote must be preceded by a
> backslash);
>
> * comments are allowed with parentheses at either end of the local-part; e.g.
> john.smith(comment)@example.com and (comment)john.smith@example.com are
> both equivalent to john.smith@example.com.
>
> In addition to the above ASCII characters, international characters above
> U+007F, encoded as UTF-8, are permitted by RFC 6531, though mail systems may
> restrict which characters to use when assigning local-parts.
>
> A quoted string may exist as a dot separated entity within the local-part, or
> it may exist when the outermost quotes are the outermost characters of the
> local-part (e.g., abc."defghi".xyz@example.com or "abcdefghixyz"@example.com
> are allowed. Conversely, abc"defghi"xyz@example.com is not; neither is
> abc\"def\"ghi@example.com). Quoted strings and characters however, are not
> commonly used. RFC 5321 also warns that "a host that expects to receive mail
> SHOULD avoid defining mailboxes where the Local-part requires (or uses) the
> Quoted-string form".
>
> The local-part postmaster is treated specially—it is case-insensitive, and
> should be forwarded to the domain email administrator. Technically all other
> local-parts are case-sensitive, therefore jsmith@example.com and
> JSmith@example.com specify different mailboxes; however, many organizations
> treat uppercase and lowercase letters as equivalent.
>
> Despite the wide range of special characters which are technically valid;
> organisations, mail services, mail servers and mail clients in practice often
> do not accept all of them. For example, Windows Live Hotmail only allows
> creation of email addresses using alphanumerics, dot (.), underscore (_) and
> hyphen (-). Common advice is to avoid using some special characters to avoid
> the risk of rejected emails.
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edited Oct 7, 2021 at 10:55
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answered Mar 21, 2014 at 12:06
Yash PatelYash Patel
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In my PHP I use this check
<?php
if (preg_match(
'/^(?:[\w\!\#\$\%\&\'\*\+\-\/\=\?\^\`\{\|\}\~]+\.)*[\w\!\#\$\%\&\'\*\+\-\/\=\?\^\`\{\|\}\~]+@(?:(?:(?:[a-zA-Z0-9_](?:[a-zA-Z0-9_\-](?!\.)){0,61}[a-zA-Z0-9_-]?\.)+[a-zA-Z0-9_](?:[a-zA-Z0-9_\-](?!$)){0,61}[a-zA-Z0-9_]?)|(?:\[(?:(?:[01]?\d{1,2}|2[0-4]\d|25[0-5])\.){3}(?:[01]?\d{1,2}|2[0-4]\d|25[0-5])\]))$/',
"tim'qqq@gmail.com"
)){
echo "legit email";
} else {
echo "NOT legit email";
}
?>
try it yourself http://phpfiddle.org/main/code/9av6-d10r
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answered Jul 23, 2015 at 2:00
Yevgeniy AfanasyevYevgeniy Afanasyev
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For simplicity's sake, I sanitize the submission by removing all text within
double quotes and those associated surrounding double quotes before validation,
putting the kibosh on email address submissions based on what is disallowed.
Just because someone can have the John.."The*$hizzle*Bizzle"..Doe@whatever.com
address doesn't mean I have to allow it in my system. We are living in the
future where it maybe takes less time to get a free email address than to do a
good job wiping your butt. And it isn't as if the email criteria are not
plastered right next to the input saying what is and isn't allowed.
I also sanitize what is specifically not allowed by various RFCs after the
quoted material is removed. The list of specifically disallowed characters and
patterns seems to be a much shorter list to test for.
Disallowed:
local part starts with a period ( .account@host.com )
local part ends with a period ( account.@host.com )
two or more periods in series ( lots..of...dots@host.com )
&’`*|/ ( some&thing`bad@host.com )
more than one @ ( which@one@host.com )
:% ( mo:characters%mo:problems@host.com )
In the example given:
John.."The*$hizzle*Bizzle"..Doe@whatever.com --> John..Doe@whatever.com
John..Doe@whatever.com --> John.Doe@whatever.com
Sending a confirm email message to the leftover result upon an attempt to add or
change the email address is a good way to see if your code can handle the email
address submitted. If the email passes validation after as many rounds of
sanitization as needed, then fire off that confirmation. If a request comes back
from the confirmation link, then the new email can be moved from the
holding||temporary||purgatory status or storage to become a real, bonafide
first-class stored email.
A notification of email address change failure or success can be sent to the old
email address if you want to be considerate. Unconfirmed account setups might
fall out of the system as failed attempts entirely after a reasonable amount of
time.
I don't allow stinkhole emails on my system, maybe that is just throwing away
money. But, 99.9% of the time people just do the right thing and have an email
that doesn't push conformity limits to the brink utilizing edge case
compatibility scenarios. Be careful of regex DDoS, this is a place where you can
get into trouble. And this is related to the third thing I do, I put a limit on
how long I am willing to process any one email. If it needs to slow down my
machine to get validated-- it isn't getting past the my incoming data API
endpoint logic.
Edit: This answer kept on getting dinged for being "bad", and maybe it deserved
it. Maybe it is still bad, maybe not.
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edited Feb 26, 2018 at 18:31
answered Jan 24, 2016 at 6:21
BradChesney79BradChesney79
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I thing this answer is downvoted because this is an opinion, and it actually
does not answer the question. Besides, users who get their email address
silently sanitized will never get emails from you. You'd better inform them
that their email address is not accepted.
– vcarel
Commented Jun 7, 2018 at 16:18
* 2
I suspect the downvotes are because there are too many ideas here. The
disallowed list, while these are useful unit tests, should be prefaced with
what is allowed. The programming approach seems relatively fine, but, would
probably fit better after you list the specs you're working with, etc..
Sections and mild copy-editing would help. Just my 2cents.
– HoldOffHunger
Commented Sep 10, 2018 at 20:13
* @vcarel - Oh, absolutely. Front-end user side validation would inform them
what rules (available from the tooltip) they were breaking. You are right--
it is an overall opinion. However, the question above is from someone that is
asking X for a Y question for sure. This is guidance and it works... not only
does it work, it works well. I don't let bullshit email addresses in my
systems where I make the decisions.
– BradChesney79
Commented Sep 11, 2018 at 13:25
* @HoldOffHunger I can see that the overall idea is not as coherently expressed
as it could be, I may revise on another day where I have more time to better
express that. Thanks for the insight.
– BradChesney79
Commented Sep 11, 2018 at 13:27
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I created this regex according to RFC guidelines:
^[\\w\\.\\!_\\%#\\$\\&\\'=\\?\\*\\+\\-\\/\\^\\`\\{\\|\\}\\~]+@(?:\\w+\\.(?:\\w+\\-?)*)+$
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edited May 19, 2017 at 20:26
answered Apr 19, 2017 at 21:02
MauMau
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1
* 1
This version improves the regex by checking the length of domain/subdomains.
Enjoy!
^[\\w\\.\\!_\\%#\\$\\&\\'=\\?\*\\+\\-\\/\\^\`\\{\\|\\}\\~]+@(?:[\\w](?:[\\w\\-]{0,61}[\\w])?(?:\\.[\\w](?:[\\w\\-]{0,61}[\\w])?)*)$
– Mau
Commented May 19, 2017 at 20:31
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Gmail will only allow + sign as special character and in some cases (.) but any
other special characters are not allowed at Gmail. RFC's says that you can use
special characters but you should avoid sending mail to Gmail with special
characters.
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answered Sep 17, 2014 at 18:22
MohammedMohammed
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Highly active question. Earn 10 reputation (not counting the association bonus)
in order to answer this question. The reputation requirement helps protect this
question from spam and non-answer activity.
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