https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342#note_17193335

We use bcc here because we don't want to generate this emails for a
thousand times. This could be potentially expensive in a loop, and
recipients would contain all project watchers so it could be a lot.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342/diffs#note_17039533

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342/diffs#note_17043090

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6342#note_16118195

This reverts commit 1404aa86.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6019#note_16956860