This repository is an exact clone of Gitlab's mail-smtp_tool gem directory. We only fork it to be able to include the gem without cloning the entire repository (which includes a lot of unneeded code and is pretty large) with bundler.
Simply clone https://gitlab.com/gitlab-org/gitlab and copy the entire /vendor/gems/mail-smtp_pool subdirectory here, overwriting all files. The .gitlab-ci.yml file can be skipped since we don't run the CI on Gitlab.