is_email() and sanitize_email() differ.

[DuisterDenHaag]

According to sanitize_email() and FILTER_SANITIZE_EMAIL and FILTER_VALIDATE_EMAIL a plus sign (+) is a valid character in an email address. Yet is_email() will fail. (info+admin@example.com)

Why is the validity for is_email() different from sanitize_email()?

Before reporting this, I found two related issues: #47467 and [48645].

Since PHPMailer is using is_email() all valid addresses with a + will result in an error.

[ayeshrajans]

is_email function does accept email addresses with the plug sign.

var_dump(is_email('info+admin@example.com'));
// info+admin@example.com

Note the function returns the original email address on email addresses this function deems correct. If the is_email function returns false for you on such email address, it is possible that a plugin makes so by using is_email filter.

[SergeyBiryukov]

Replying to ayeshrajans:

is_email function does accept email addresses with the plus sign.

var_dump(is_email('info+admin@example.com'));
// info+admin@example.com

Just noting that I was able confirm, is_email() does treat this address as valid.

[desrosj]

53130.diff​ adds a test for an email with a +. I think it doesn't hurt to add to show it works (and continues to work).

[desrosj]

In 50812:

Formatting: Verify emails with + characters are valid.

This adds an assertion to confirm that is_email() considers email addresses with a + valid.

Props SergeyBiryukov, ayeshrajans.
Fixes #53130.