The current guide will help you to solve the problem of ignoring emails when received on the Helpdesk because of the auto-generated (auto-submitted) header loop problem.
The logs (either production.log or redmine_helpdesk.log files) could contain some error message similar to this one:
ignoring email with Auto-Submitted:auto-generated header
It is correct behavior by now that the Helpdesk plugin filters messages that contain auto-generated headers because to avoid cyclic auto-loop between servers. That's why there is no way to switch this function off via the Redmine interface.
To disable header checking functionality you need in file plugins/redmine_contacts_helpdesk/app/models/helpdesk_mail_support.rb to find method:
def ignored_helpdesk_headers helpdesk_headers = { 'X-Auto-Response-Suppress' => /\A(all|AutoReply|oof)/ } ignored_emails_headers.merge(helpdesk_headers)` end
And change it to:
def ignored_helpdesk_headers {} end
Afterward please restart the webserver.