How many @ symbol can be in an email address?

Question

Is there any rule for having a specified amount of @ symbol in any email id. Just come to my mind if we're to check if an email id is valid or not using PHP.

As far as I'm aware, you can only have one. The @ symbol is the delimiter between the domain name and the address name; multiple @ symbols would very likely confuse the email parser. — Palladium, Sep 10 '12 at 16:33

score 40 · Accepted Answer · edited May 23 '17 at 12:16

40

If enquoted multiple @ are allowed. I have to ask why do you need this information. Please please please do not try to write a regex / function or whatever to validate emailaddresses. You have to worry about 3 rfc's (and perhaps 4 if you want to take into account unicode). And you will fail and it will drive you mad.

See my previous answer for more information and a regex you may use if you have an older version of PHP

P.S.

In case someone missed my point: do not try to come up with some validation of your own to validate emailaddresses yourself "ever".

edited May 23 '17 at 12:16

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answered Sep 10 '12 at 16:35

PeeHaa

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Double checking here, you mean for '@' signs in the *username* there can be multiple right? There can't be an '@' in the domain can there? The reason I ask is for obtaining hostnames from submitted emails to check mx records, is as far as I know, the standard validation scheme. – Jamie Marshall Dec 13 '20 at 19:55
Following your last point... Rather than spend the time attempting to validate an address with regex etc, the norm is to send the address in question an email with a link to validate. The end user clicks the link and this serves as validation that 1) the email address is real and exists and 2) is also actively used (relatively speaking) and accessible by the user. From a database perspective, a validation key can be stored alongside the user account along with a flag of invalid or valid state. – ThisClark May 25 '22 at 15:18

score 26 · Answer 2 · edited Oct 07 '21 at 05:49

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There can be any number (within the size limits of an email address) except that the last one must be the separator between the domain name and the "local part".

If an @ or any other "unusual" characters (as defined by RFC 5322) exist in the local part it MUST appear in quotes, e.g: "user@something"@example.com

edited Oct 07 '21 at 05:49

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answered Sep 10 '12 at 16:34

Alnitak

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score 19 · Answer 3 · answered Sep 10 '12 at 16:34

19

There is no specific limit on @ characters.

"very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com is a valid address.

See also, the Wikipedia page on the subject.

answered Sep 10 '12 at 16:34

Quentin

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score 1 · Answer 4 · edited Oct 07 '21 at 06:15

An addr-spec is a specific Internet identifier that contains a locally interpreted string followed by the at-sign character ("@", ASCII value 64) followed by an Internet domain. The locally interpreted string is either a quoted-string or a dot-atom. If the string can be represented as a dot-atom (that is, it contains no characters other than atext characters or "." surrounded by atext characters), then the dot-atom form SHOULD be used and the quoted- string form SHOULD NOT be used. Comments and folding white space SHOULD NOT be used around the "@" in the addr-spec.

See :- https://www.rfc-editor.org/rfc/rfc5322#section-3.4.1

score 1 · Answer 5 · answered Sep 10 '12 at 16:46

My real question is would it make sense to have two @ symbols in an email?
How would it work?

I would use filter_var() with FILTER_VALIDATE_EMAIL. Below is a sample use and outputs,

function testemail($email) {
    echo "'$email' => ";
    var_dump(filter_var($email, FILTER_VALIDATE_EMAIL));    
    echo "<br />";
}

testemail('');
testemail('myemailsample.com');
testemail('myemail@sample');
testemail('myemail@sample.com');
testemail('myemail@@sample.com');
testemail('myemail@sa@mple.com');

Output,

'' => bool(false)
'myemailsample.com' => bool(false)
'myemail@sample' => bool(false)
'myemail@sample.com' => string(18) "myemail@sample.com"
'myemail@@sample.com' => bool(false)
'myemail@sa@mple.com' => bool(false)

"My real question is would it make sense to have two @ symbols" If the spec allows it it does. Although one could argue about the wtfness of the specs. — PeeHaa, Sep 10 '12 at 16:47
And so it seems to be true, '"my@email"@sample.com' => string(21) ""my@email"@sample.com" — Jared Paolin, Sep 10 '12 at 16:55

score 0 · Answer 6 · answered Sep 10 '12 at 16:34

0

To check for a valid email adress I should use the filter_var function. It will validate the string and return true or false. You don't have to think about regular expressions.

answered Sep 10 '12 at 16:34

Jordi Kroon

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How many @ symbol can be in an email address?

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