Assume that you have a third-party archiving software running for Microsoft Exchange Server 2010. In this situation, Personal Retention tags that were set on folders are periodically reset to the default retention policy after the Managed Folder Assistant runs.
This is a known issue in Exchange Server 2010. If third-party software calls the IMAPIFolder::CreateFolder() function and passes the OPEN_IF_EXISTS flag, the PR_RETENTION_FLAGS and PR_COMMENT fields on the folder will be overwritten. This causes the Personal Retention tags to be reset to the default retention. For more information about the CreateFolder function, see IMAPIFolder::CreateFolder.