Install postfix and update APT cache as part of the Docker image build
Meaningless commit per request by @bitemyapp
Revert "Meaningless commit per request by @bitemyapp"

This reverts commit eaabcb1db84c06d7584227ee26c9f6a6f5264f41.
Merge pull request #276 from teozkr/docker-postfix

Install postfix and update APT cache as part of the Docker image build