Exchange Rules Migrator
This PowerShell script was originally developed when I was working in an Exchange support team at Microsoft. When an Exchange mailbox is moved between different forests, any saved inbox rules which refer to mailboxes internal to the user's forest will break, because intra-forest rules default to the LegacyDN format, which looks like
[EX:/distinguished/name], rather than regular SMTP addresses.
This script connects to the user's current mailbox to determine the primary SMTP address for every LegacyDN reference in the mailbox's inbox rules. It then updates the rule on the server with the correct SMTP address, thereby mitigating the rules-breaking consequence of moving a mailbox between forests.
This script relies on the user having PowerShell access to their Exchange mailbox. Details on accessing Exchange over PowerShell may be found here.