Released: March 2023 Exchange Server Security Updates

Mr_Chris We are definitely not aware of this problem. The exception you are getting is not something that we have seen (and upon a bit of review, seems to relate to code that we did not touch for a while) so it is definitely a mystery as to what is going on. Could I ask you to open a ticket with our support. If you do, please PM me the ticket number as I have someone who is super curious to find out why this would be a thing.

The initial thinking is that it seems to have to do with some files in C:\Program Files\Microsoft\Exchange Server\V15\Logging\MailboxAssistantsLog or possibly the ...\V15\Logging\Query\ (or whatever the install path is on your server). Can you just quickly check if you are maybe running out of space or... maybe check your system log for any disk/file system related events? It is possible (and I am not claiming it is) that something is going on with file system on this particular drive and that is why some files are having issues.