Released: July 2021 Exchange Server Security Updates

Anthony Mazzeo - As of right now, I am not aware of the need to pull the updates or anything like that. There are several things that are going on here, and it is very important to be super precise with actual errors that are seen. I have been replying to various Reddit threads and both Lukas and I have been all over comments here on the blog but - in short there are 3 major buckets of issues related to OWA and/or ECP after installation of SUs.

1. Not installing manually downloaded updates from elevated CMD prompt. All discussed here.
2. Issues with OAuth certificates. This is actually not a new problem (it has been discussed a while ago). We have changed the blog post to include all the steps needed to check that the certificate is in good shape before installing SUs, and if not, this is the article to follow. But yes - certificate propagation to all servers can take some time.
3. Issues with servers that are a part of some sort of Load Balanced setup. The way to handle this is to take servers out of the LB pool for patching and/or apply updates to all servers in the LB pool at the same time; once they are all updated, issues will go away (based on what we have heard from customers). There can be variability here because variety of 3rd party solutions can be in use.

I am not aware of other scenarios that cause issues; there could be some, but not aware of anything else that has been confirmed that is not caused by one of the 3 things above. Errors and experience will differ slightly based on what is going on.