smptplib problem SMTPRecipientsRefused for emails with ! exclamation mark in local portion of email

[radzhome at gmail.com]

smtplib.SMTPRecipientsRefused: {'aahlin!@gmail.com': (550, 'restricted characters in address')}

As in this question, the answer has reference to RFCs that spec it out, and state that exclamations are ok, so why is smptplib throwint this error?

http://stackoverflow.com/questions/2049502/what-characters-are-allowed-in-email-address

Django uses smtplib to send emails so it in turn fails too but email validation allows you to enter !