Processing archive mailbox x failed with error

[svallance]

We're running the latest version of Veeam for M365, 6.0.0.385 and we're seeing some issues with some of the mailboxes in our backups.

Processing archive mailbox xxxx@xxxx failed with error: Failed to synchronize item changes in folder: XXXX.. The mailbox operation failed.

We've had a case open (Case # 05504958) for a couple of weeks now but we haven't been able to resolve it. The latest info from support is they're currently noticing a trend in cases with a similar issue.

Are there any known issue impacting processing for some mailbox folders?

[Mike Resseler]

This looks like an archive mailbox? Is it only with archive mailboxes or also with regular mailboxes? We do know that sometimes the synchronization issues exist, but that can be solved by clearing a cache (the same can actually happen when you use Outlook in cached mode)

[svallance]

This is only happening to archive mailboxes.

We tried moving the users we're seeing this on into a new job and ran the full synchronization command from PowerShell.

Is there another way to clear the cache we can try?

[svallance]

I should mention we also tried setting up a new repository and backing up just those user's archive mailboxes to it, but the first time the new backup ran they still failed.

[Mike Resseler]

Let me ping support leadership to see what is going on. I kind of fear it is an issue on the MFST side. Especially if it is always the same users their archive.

[svallance]

We've been trying to get this resolved for a while now. Our customer decided to try KeepIt to compare their options, and that has been working flawlessly according to them. They don't have any of these errors backing up the archive mailboxes which seems to point to this being a Veeam-specific issue.

We'd really like to keep this customer obviously but it's not looking like we'll get anywhere with support before they decide to cut their losses...

[Mike Resseler]

Thanks for letting me know. I am aware that are support is working together with MSFT at this point in time.