SMTP can be blocked at ISPs to prevent spammers.
Use a shell script with this [[ssh access to a remote machine|e/01013]].
$ cat /usr/sbin/sendmail #!/bin/sh ssh sg.webconverger.com /usr/sbin/sendmail "$@"
This is a less suckier solution than running msmtp or esmtp, since you rely on your ssh credentials, not some saved password on your filesystem.
You can configure mutt MUA to use a specific sendmail binary like so:
$ egrep sendmail .muttrc set sendmail = "/home/hendry/sg-sendmail"