SlackBuildsOrg/network/msmtp

msmtp is a simple SMTP client.

In the default mode, msmtp transmits a mail to an SMTP server (for
example, at a free mail provider) which does the delivery.

To use this program with your mail user agent (MUA), create a
configuration file with your mail account(s) and tell your MUA to call
msmtp instead of /usr/sbin/sendmail.

libgsasl is an optional dependency.