a forum user made me aware that on our forum, the signup mail is not arriving. This could be related to a recent update. So I updated again yesterday evening to latest master and the problem persists.
Mails work as expected, but Discourse does not send mails for signup or on ‘send activation mail’ from the admin interface. There is no entry in the sent mails log and no entry in the Discourse error log. However, notifications on replies are sent out as expected. The mail testing in the admin interface works as well.
I hope I just missed a setting somewhere. Otherwise, this is a bug and should be refiled accordingly.