Gmail dot blindness

Gmail cannot recognize dots or periods in email addresses or the user names - that means an address like "abc.xyz@gmail.com" is the same as "abcxyz@gmail.com" or "a.b.cxy.z@gmail.com".

If a Gmail account like "abc.xyz@gmail.com" already exists, registration of "abcxyz@gmail.com" or any address with string "abcxyz"(charters may be separated with random pattern or sequence of dots) would fail.

This is actually a bug than a feature but you can again exploit it to have different kind of email address in your forum signatures.

Keep in mind that hyphens (-) and underscores (_) can't be used in a Gmail address. Also, gmail user names are case insensitive, so it doesn't matter if you enter upper case or lower case letters.