Note that koji-gc sends its own notifications, unless you pass --no-mail. Granted I think a number of instances do run it that way.

It sends own notification only in case of moving to trashcan (in handle_trash) If build stays in some tag after ontagging, no mail is sent.

PR #691

Commit 82907196 fixes this issue

Commit b667f73c fixes this issue

This issue has been migrated to Fedora Forge:
https://forge.fedoraproject.org/koji/koji/issues/690

Please continue any further discussion there.