Enable this to install as system-wide MTA

Packages describing “mta” as local USE flag

Package “mta” Flag Description
mail-mta/msmtp Enable this to install as system-wide MTA
mail-mta/opensmtpd Enable this to install as system-wide MTA
mail-mta/ssmtp Install symlinks for sendmail-compatible MTA.
sys-process/fcron Enable mta support for sending emails from fcron