➜   telnet abc.net 25
Trying 88.00.00.243...
Connected to abc.net.
Escape character is '^]'.
220 mail.abc.net ESMTP Postfix
EHLO def.net
250-mail.abc.net
250-PIPELINING
250-SIZE 20480000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH PLAIN LOGIN CRAM-MD5
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
MAIL FROM:foo@abc.net
250 2.1.0 Ok
RCPT TO:bar@xyz.net
554 5.7.1 <bar@xyz.net>: Relay access denied