man mprobe (Administration système) - smtp-server aliveness probe

NAME

mprobe - smtp-server aliveness probe

The mprobe(8 zm) is usable to test, if the named host (no IP address allowed!) has a smtp-server, that responds properly.

0: All is well, smtp-server responded just fine
2: Can't resolve target hostname
3: mprobe(8 zm) internal failure, can't create socket (should not happen!)
4: failed to connect to the remote host
5: mprobe(8 zm) internal failure, fdopen() failed.. (should not happen!)
17, 19: The remote smtp-server hung-up on us, most likely
18: The remote smtp-server did respond something, but it did not begin with "220"
20: Timeout (60 seconds) from start of processing.
99: Missing mandatory host parameter.

This tool is authored and copyright by: Matti Aarnio <mea@nic.funet.fi>