Docker smtp images

• namshi/smtp: exim4 light & buster, last updated 2019-11, autobuilds, Pulls10M+ no volumes: persistence ?
• freinet/postfix-relay: postfix, stretch, s6, last updated 2019-11

Outdated

• applariat/tx-smtp-relay: Used by halkeye/postfix helm chart No Dockerfile found, last Update 2016!
• cloudposse/postfix: ubuntu:14.04, updated 2y ago, no builds.
• catatnight/postfix: Updated 4 years ago, ubuntu:trusty