[root@localhost ~]# telnet mail.domain.com 25
Trying 192.168.50.241...
Connected to mail.domain.com.
Escape character is '^]'.
220 mail.domain.com ESMTP ready
ehlo mail.domain.com
250-mail.domain.com
250-AUTH PLAIN
250 AUTH PLAIN
mail from: [email protected]
250 2.0.0 OK
rcpt to: [email protected]
554 5.7.1 <[email protected]>: Relay access denied