SendMail: Connection refused by [127.0.0.1]

Solution 1:

Sendmail passes messages submitted by "send via command line sendmail" to local sendmail daemon listening at 127.0.0.1:25.

It seems that you sendmail listens only on IPv4 192.168.0.1:25 (local network?) and IPv6 ::1:25 (any). Most likely you wanted to accept incoming TCP connections only from local network.

Fix DAEMON_OPTIONS in your sendmail.mc file. Add listening on 127.0.0.1 or use listening on IPv4 "any".

In your sendmail.mc add the second DAEMON_OPTIONS listed below.
Recompile sendmail.mc into sendmail.cf and restart (or HUP) sendmail daemon.

DAEMON_OPTIONS(`Port=smtp, Addr=192.168.0.1, Name=MTA')dnl
DAEMON_OPTIONS(`Port=smtp, Addr=127.0.0.1, Name=MTA-loopback')dnl