Email Validation is not RFC5321 compliant

[jayesbe]

Issue Summary

Email addresses where the local part end in a period are being flagged as invalid even though they are RFC5321 compliant.

This comment from seven years ago defines the issue fairly well

https://www.php.net/manual/pt_BR/function.filter-var.php#112492

Copying here to make it easier.

I found some addresses that FILTER_VALIDATE_EMAIL rejects, but RFC5321 permits:

<?php
foreach (array(
        '[email protected]',
        '(comment)[email protected]',
        '"this is v@lid!"@example.com',
        '"much.more unusual"@example.com',
        'postbox@com',
        'admin@mailserver1',
        '"()<>[]:,;@\\"\\\\!#$%&\'*+-/=?^_`{}| ~.a"@example.org',
        '" "@example.org',
    ) as $address) {
    echo "<p>$address is <b>".(filter_var($address, FILTER_VALIDATE_EMAIL) ? '' : 'not')." valid</b></p>";
}
?>

Results:

• [email protected] is not valid
• (comment)[email protected] is not valid
• "this is v@lid!"@example.com is not valid
• "much.more unusual"@example.com is not valid
• postbox@com is not valid
• admin@mailserver1 is not valid
• "()<>[]:,;@"\!#$%&'*+-/=?^_`{}| ~.a"@example.org is not valid
• " "@example.org is not valid

The documentation does not saying that FILTER_VALIDATE_EMAIL should pass the RFC5321, however you can meet with these examples (especially with the first one). So this is a note, not a bug report.

Technical details:

sendgrid/php-http-client 3.10.7 sendgrid/sendgrid 7.6.0 using PHP.

So the issue is we have users in our system that do have email addresses where the localpart ends in a period. This email address is being flagged as invalid even though it should be perfectly find to send an email to.

I guess the question is, does sendgrid support the above email addresses that are valid according RFC5321 ?