Exchange 2016 CU22 after login to OWA, it will flash back to login page for a few time

Brass Contributor

Newbie to exchange here. Over last week we upgraded our exchange server from cu18 to cu22 and with January 2022 SU installed. 


Upon restarted the server, user successfully login to OWA but immediately it will redirect user back to login page. It takes like 6 to 7 attempt before user can finally use OWA to read and send email. 


Strangely after a few minutes, user will be prompt back to login page and same thing happen over and over again. Could someone shed me some light on what to be check. 

1 Reply

@Don_Vlogeer Hi, just wanted to give you some belated moral support here.  FYI, I just witnessed the exact same symptoms as you described after we installed the Security Update For Exchange Server 2016 CU21 (KB5012698).  More specifically, we have 8 servers which are load balanced, and as soon as the update was installed on the first couple servers (and they were rebooted), the load balanced FQDN presented all the symptoms you described.  If we went to the direct server FQDN + /owa (or + / ecp), no issue.  Also if we looked at the load balanced FQDN and added the healthcheck.htm path to any of the virtual directories (e.g. we were getting back 200-OK's from all 8 servers, on all the virtual directories.


In the end the solution was simply to finish installing the update on the remaining servers.  Once done, the issue magically disappeared.  We had contacted MS Support for a critical Sev A case since we had the option and users were impacted / it was late.  They were quick to get in touch, but we had already finished by then.  They were pretty much in disbelief and assumed one of the servers must be the culprit.  But no, the issue is gone and there is no 1 or 2 servers that had an issue.  The culprit was 100% that not all 8 servers were the same.  Not sure beyond that on the details, but this is how it played out.  Likely some sideways server-to-server proxying not working or something along those lines.  Very strange, kind of annoying, yet was amazing that the issue was so persistent and then just bam/gone.


Hopefully you had similar luck.