Microsoft plans to remove the management of Exchange transport-rule based policies from the classic EAC in mid-2022. Given that Microsoft 365 DLP policies offer the same if not better functionality for Exchange Online and can process other workloads as well, it's a good time to consider transitioning away from the older technology. Microsoft is obviously not putting any engineering effort into Exchange-based DLP, so there's no good reason not to move over and use the technology they are investing in, The transition will take time and effort, but it will be worth it.
Exchange Server 2010 treats some object attributes differently than Exchange Server 2003. The most common issue that this causes is invalid aliases on mailbox users.
During the co-existence period of a transition from Exchange Server 2003 to Exchange Server 2010 you may encounter an issue with the legacy Outlook Web Access URL redirection.
The Exchange Profile Analyzer is used to collect statistical information about the Exchange organization that is helpful for understanding the size and makeup of the Exchange data that is to be migrated. When migrating from Exchange Server 2003 to Exchange Server 2010 this information is invaluable and should always be collected during the planning phase of the project.