Microsoft has released security updates (SUs) that resolve vulnerabilities found in:
Exchange Server 2013
Exchange Server 2016
Exchange Server 2019
IMPORTANT: When manually installing SUs...
Updated Mar 16, 2022
Version 6.0
Blog Post
We have a complex environment with 2013, 2016, 2019 versions, and separated roles on 2013. So far the problem appeared on 2013 and 2016, 2019 has not been affected. We managed to remove the previous expired federation certificate and clean the arbitration mailbox for few times.
It looks like the problem still occurs on 2013 mailbox servers after exactly 24 hours since last mailbox cleanup. So I cannot see this "solution" to remove expired certificates and cleaning the mailbox as a fully functional solution. Looks like it gives only temporary help for us.
Also, it is not sustainable either to demand that certificates must be valid for more than 30 days, otherwise your servers will crash.
We need proper fix for this mess asap.