I will be migrating uses from one E2K3 forest to a E2K7 forest. My steps will be first to use ADMT, to migrate the user. Then use the Move-mailbox command. For this I am not sure if I should use the -allowmerge or -NTAccountOU option. I tested this earlier and the -NTAccountOU created a account during the move-mailbox step. This was an issue because I already had the account when using the ADMT. Once this is completed I will use GalSync.
Please let me know which options would work best.