How to pause throttling and blocking of out-of-date on-premises Exchange Servers

Andreas_W70 thanks for reporting that really odd behavior RE prod.outlook.com servers that aren't yours. We found that a recent report code update inadvertently exposed this issue WRT messages that route out->in again, e.g. scenarios like a signature service, just like you surmised good sleuthing! Rest assured that none of your mail is subject to enforcement, it's just a UI bug. We've got a fix rolling out this week so if you're still seeing the erroneous servers by early next please DM me to let me know. 

Kriskost it's not yet possible to create an alert policy for this. We've got it on our backlog to hopefully address by this fall. The Get-OnPremServerReportInfo shows only current or historically out-of-date server records - it does NOT show the build number of any server that's current up-to-date. 

TobiaScapin >>why these blocked messages are not present in Mail Flow > Message Trace?

it's by design. The messages / connection is blocked at the EXO edge, before we accept the messages. For them to show up in EXO Message Trace they need to be accepted into the service - but they aren't, they're rejected at the edge. So you'll only see both temp errors and perm (block) errors in your on-premises Message Tracking Logs, not in EXO Message Trace.

 NervyWreck Thanks for getting up to date with 2019! Unfortunately if the 2019 and 2013 servers have different names then the 2013 server is 'orphaned' as we have no way to know that the 2019 server replaced it. However, since your 2013 server isn't sending mail any more you can use the "Active, Inactive" filter in the report to filter out "inactive" servers like this 2013 one. Inactive is based on the number of days specified for which no messages have been received by EXO from that server - by default Inactive is if the last message received from the server was > 3 days ago, but you can customize it for fewer or more days. 

Best wishes,

Kevin Shaughnessy
Principal Product Manager | Exchange Online