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 and gnome-keyring are optional dependencies.