Most 554 relay access denied related news are at:
More 554 relay access denied related news:
Postfix SMTP Authentication and Dovecot SASL for RHEL/CentOS 6 linuxmail.info 1 Aug 2011 | 12:28 am
SMTP Authentication (SMTP Auth) provides an access control mechanism that can be used to allow legitimate users to relay mail while denying relay service to unauthorized users, such as spammers. Conf...