This is some detailled information regarding the mail support outage occuring on the 16th of November starting around 3pm CET
and was solved 17th of November around 7:30 am CET.

Timeline:

• starting point was, that emails weren’t relayed any more from support@meisterplan.com to support@meisterplan.zendeks.com
• the mails sent to meisterplan.com were directly returned with an error message saying that relaying maisl was prohibited by the
  recipient
• we opened an Office365 Support case around 7pm CET - we got information from the support case over the night
• we implemented the remediation and the problem was solved around 7:30 am

Description:

• Microsoft apparently changed their Anti-Spam settings and email relaying was no longer possible as default
  setting in the Anti-Spam rules
• our Off365 config was not the problem - a new rule on top of that was preventing relaying mails ...
• Microsoft support told us where to set the respective value - and as always it was one checkbox ..
• nevertheless - this was a major side effect of an internal change at Microsoft - the first of this kind since we use Off365

We are talking about 24 failures that we didn't were able to deliver to support@meisterplan.zendesk.com - 20 of them were internal and test emails.