SMTP Error 501 5.5.4 Invalid Domain Name


  • Used Zammad version: 3.1.0
  • Used Zammad installation source: deb-package
  • Operating system: Ubuntu 18.04
  • Browser + version: Firefox + Vivaldi latest

Expected behavior:

  • Tried to configure our Exchange 2016 server as IMAP+SMTP. With a successful integration.

Actual behavior:

  • After setup of SMTP, the message “Error 501 5.5.4 Invalid Domain Name”

Steps to reproduce the behavior:

  • nginx is configured to server infra-zammad-01
  • Log File shows no error both from Zammad instance as from the Exchange Server.
  • SMTP works with several other services
  • Domain request is enabled on the Exchange Server 2016

Please check your mail server logs again.
Possibly the above is triggered by auto testing.

Wihtout knowing why error 501 comes, it’s impossible to help.

We found the Problem.

The FQDN in Zammad (Settings => System) had a space in it. This isn´t allowed with Exchange.
The next problem was that the Testmail was send to the Inbox, but we setup an own Folder, which was only checked.

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