Package ssmtp-docs: Information

extremely simple MTA to get mail off the system to a mail hub
A secure, effective and simple way of getting mail off a system to your
mail hub. It contains no suid-binaries or other dangerous things - no mail
spool to poke around in, and no daemons running in the background. Mail is
simply forwarded to the configured mailhost. Extremely easy configuration.
WARNING: the above is all it does; it does not receive mail, expand aliases
or manage a queue. That belongs on a mail hub with a system administrator.