Virtual package mail-transport-agent is provided by:
dpkg-query: no packages found matching courier-mta dpkg-query: no packages found matching dma dpkg-query: no packages found matching esmtp-run ||/ Name Version Architecture +++-==========-==========-==================================== un postfix <none> <none> (no description available) ii ssmtp 2.64-11 amd64 extremely simple MTA to get mail off the system to a mail hub 2 packages