How to move mail between servers

Two completely different servers, in different domains.

SERVER1 in DOMAIN1.LOCAL (responsible for, say, MYCOOLDOMAIN.COM mail).
SERVER2 in DOMAIN2.LOCAL (responsible for, say, MYOTHERCOOLDOMAIN.COM mail...or maybe not could become responsible for MYCOOLDOMAIN.COM mai!).

Create secondary Domain Admin accounts in both domains (eg Admin2).

Give Admin2 Full Control to everyone's mailboxes (this is a right that is denied to the built-in Admin account).

Download EXMERGE and locate the extracted files in the BIN folder for Exchange (otherwise a DLL error).

In Domain1, logon as Admin 2. Run EXMERGE and extract each users mailbox to a PST.
In Domain2, logon as Admin 2. Run EXMERGE and import each users mailbox to a PST.

Often the last step wil faill, so an alterative is to add the PST as a Personal Folder in Outlook and merge the PST into the mailbox.