System Administration Guide: Network Services

How to Verify Connections to Other Systems

The mconnect program opens a connection to a mail server on a host that you specify and enables you to test that connection. The program runs interactively, so you can issue various diagnostic commands. See the mconnect(1) man page for a complete description. The following example verifies that mail to the user name sandy is deliverable.

% mconnect phoenix

connecting to host phoenix (, port 25
connection open
220 ESMTP Sendmail 8.13.1+Sun/8.13.1; Sat, 4 Sep 2004 3:52:56 -0700
expn sandy
250 2.1.5 <>

If you cannot use mconnect to connect to an SMTP port, check these conditions.