Messages resent after exchange move to different domain

[kevdude]

We had to move the exchange server to a different domain for forest joining reasons, duplicate netbios names in the same domain, long story.
After the move, about a weeks worth of email was resent, almost like it was being held in queue, so we ended up with a lot of duplicates. All the messages were sent outside the system. (internet) I'm not sure if it happened with a lot of people or just the hand full of people that informed us about it. Things seem to be fine now, but we don't really know until we're informed about it.
Any Ideas would be greatly appreciated.

Thanks