Exchange 2010 Sp3 Rollup 10. We have a retention policy applied to the Conversation History folder and is applied to all the user mailboxes and removes message over 30 days old. This works for the majority of mailboxes but not all. I found a common thread for the mailboxes that the policy does not work. We have a Hybrid configuration with Office 365 and these non-working mailboxes have moved out to Office 365 and have moved back on-prem.
The policy appears to be applying to the mailbox at least in as far as showing the expiration on each email in the folder, but the removal still doesn't work.
I removed policy, started the managed folder assistant, waited, applied again, repeat. Nothing has worked. I looked at the user object to compare a mailbox that retention works and the one that doesn't and I don't see anything that is sticking out as a problem. Could there be something in the mailbox that is prevent this policy from actually removing messages?