I have Postfix set up using virtual domains with sasl enabled such that to send an e-mail they need to login with "usern...@domain.com".
As it is, however, when a user logs in to the smtpd, they can thereafter treat my mail server as an open relay & forge their "Mail From" address to come from anything, even another user on the mail server. Is it possible to have postfix reject any "Mail From" address which is different than the one they used to log in with?
