I don't have a local SMTP server installed, but I heard sendmail command can do the favour for me, but seems I encountered a problem...

```
/usr/lib/sendmail -v foo@example.com  < /etc/hosts
foo@example.com... Connecting to [127.0.0.1] via relay...
foo@example.com... Deferred: Connection refused by [127.0.0.1]

```