http://email.about.com/od/emailbehindthescenes/f/address_length.htm

Yes, the maximum length of an email address is 256 characters.

Every email address is composed of two parts. The local part comes before the ‘@’ sign, and the domain part follows it. In “user@example.com”, the local part is “user”, and the domain part is “example.com”.

The

local part must not exceed 64 characters and
the domain part cannot be longer than 255 characters;
the total combined length of all characters (including ‘@’ and punctuation) must not exceed 256 characters, however.
In sum, an email address can be 256 characters long at most. When you create an address, make sure your user name has less than 65 characters.