There are situations where messages configured to strip are not stripping in a specific folder, but if those messages are moved to a different folder, then they do strip properly.
There are situations where a message will not strip properly when in one folder, but will when moved to a different folder. One potential reason for this is due to the fact that the Folder in the Exchange mailbox is experiencing corrupton which affects the stripping process.
When you witness corrupt folders within Exchange mailboxes that are preventing the stripping policies in Archive Manager from working you have two potential workarounds.
1. Move the messages into a different folder that is not experiencing corruption.
2. For a more permanent solution, move the Exchange mailbox to a different information store. You can either leave the mailbox at the new information store or you can move it back to the original information store once it has been completed. Moving the mailbox forces the mailbox to get recreated on the new store which will rebuild all the folders. This results in folders that are not corrupt that work flawlessly in the stripping process.