Possible Duplicate:
Exceeding Max Email Address Sizes
Is there a technical limitation to how long email addresses can be? Are there practical limitations imposed by the different major email providers out there (Google, Microsoft, etc.)?
De jure or de facto, is there a limit on the number of characters in an email address?
What is the maximum length of an email address?
254 characters
"This arises from the simple arithmetic of maximum length of a domain (255 characters) + maximum length of a mailbox (64 characters) + the @ symbol = 320 characters. Wrong. This canard is actually documented in the original version of RFC3696. It was corrected in the errata. There's actually a restriction from RFC5321 on the path element of an SMTP transaction of 256 characters. But this includes angled brackets around the email address, so the maximum length of an email address is 254 characters." - Dominic Sayers
-> https://web.archive.org/web/20130710170052/http://www.eph.co.uk/resources/email-address-length-faq/