Sometimes the simple tricks are the best:

machine:~ > telnet hostname 25
Trying 192.168.0.1...
Connected to hostname.
Escape character is '^]'.
220 hostname.domain ESMTP Postfix
QUIT
221 Bye
Connection closed by foreign host.

compare to:

machine:~ > telnet hostname 25 | tail +4
220 hostname.domain ESMTP Postfix
QUIT
Connection closed by foreign host.
221 Bye

I'm not sure you won't still have line vs character mode issues, but it might help.