"Smail would be ideal for any situation where complex
routing, filters and features (virtual users etc.) are not
required. I’ve used it on many a desktop or laptop system
where I’ve been developing projects that require a local MTA.
I’ve also deployed it on smaller servers that do not provide
SMTP to their respective clients. In these cases I needed something
to forward locally-produced error messages, cron-job feedback and
backup notifications to a remote address (mine)."