TYPO3 Core

In #19466 validEmail was changed to native PHP filter function.

PHP 5.2.0 upwards matches RFC 2821/2822 but still (current trunk) ignores RFC 5321:

4.5.3.1. Size Limits and Minimums
[...]
4.5.3.1.1. Local-part
The maximum total length of a user name or other local-part is 64
octets.

4.5.3.1.2. Domain
The maximum total length of a domain name or number is 255 octets.

4.5.3.1.3. Path
The maximum total length of a reverse-path or forward-path is 256
octets (including the punctuation and element separators).

As long as PHP dont check if an e-mail address is usable by smtp (and does not exceed its lenght limit) TYPO3 should check this

PHP 6 trunk (line 472)
http://svn.php.net/viewvc/php/php-src/trunk/ext/filter/logical_filters.c?revision=288084&view=markup

RFC 5321, Section 4.5.3.1. Size Limits and Minimums
http://tools.ietf.org/html/rfc5321#section-4.5.3.1
(issue imported from #M11888)