Redmine

I think I've run in to the same bug with our 3.0.3 instance; mail is definitely being sent for some circumstances, but through some combination of acting through the UI and also responding via direct email replies, the log tail is showing "MailHandler: ignoring email with Auto-Submitted:auto-replied header". I've confirmed this is happening using both local sendmail and Gmail SMTP.

It seems like a workaround might go in app/models/mailer.rb to allow config/settings.yml:mail_from config to override that value to at least allow users to skip the mail_handler.rb validation.

As best I can tell, it looks like once the header has been added, whether by Redmine or by an external mail server (e.g. #16190), Redmine will just skip sending of some emails...data does make it in, attaches to correct ticket, etc. but no notice is happening.