Drapetomaniac

I filed a bug with Joomla about not accepting email addresses like testthis+symbol@example.com during install. My explanation was “e-mail systems accept this.” The initial response was “just because some systems accept it, doesn’t mean it is valid.”

True enough. Then again, if you restrict an email address, it doesn’t mean that restriction is valid.

I’m usually more specific in reporting bugs, but frankly I was ignorant as to whether or not it was valid when I filed the bug.

Plus symbols are valid.

RFC 822, 3696, 2822 and 2821 all refer to the standards for e-mail addressing. RFC 822was passed in 1982.

3696 summarizes:

“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.”

Some good blog entries in plain English:
Email Address Format Myths
I Knew How To Validate An Email Address Until I Read The RFC
How to Find or Validate an Email Address

I have seen a lot of one line e-mail validators. If you want to see how off these are, check out Paul Warren’s partial example.