Microsoft has released security updates for vulnerabilities found in:
Exchange Server 2013
Exchange Server 2016
Exchange Server 2019
All versions (Cumulative Update levels) are impacted. ...
Updated Aug 05, 2021
Version 15.0
Blog Post
After installing Exchange 2019 CU 10 SU, my lab PCs can't connect to through outlook, and OWA and ECP goes back to login screen immediately.
My lab environment has a F5 Big-IP (ver 15.x.x.x) and 2x Exchange 2019 DAG servers, and using Exchange 2016 iAPP.
To fix the problem, just like georgedaly explained,
Login to F5 BIgIP, Local Traffics-> Virtual servers -> find VS that was created by the exchange iAPP, there should be one for http and one for https, for example xxxxx_combined_http and xxxxx_combined_https. Goto each VS's properties -> resources -> set "default persistence profile" to "source_addr", yes do it for both VSes.
Note that if you re-configure the iAPP the change will get lost, so be sure to add it back.
Hopefully M$ fix this on the next CU.