2 Exchange servers with users moved from one to the other in same building not receiving mail from origial server.

A couple of weeks ago I moved 6 users from one domain and exchange server 2003 to another domain and exchange server 2003.  (Both servers in same closet and have there own firewall) All email works out to the real world and back, and internally for both exchange servers except when  a user from the origianl server (where the email and users originally received there email)  trys to send email to the 2nd server Y where they now receive email.  Example:  abc.com, efg.com, xyz.com & 123.com were originally on the X SBS 2003 server.  Users from abc.com and  xyz.com were moved to Y SBS 2003 server.  So when a user from 123.com or efg.com try to send email to abc.com or xyz.com it  shows  up in the sent items and it is not in the  outbox and they never get an undelieverable message.   They just never get it??  Is it possible that the original SBS server X is hanging onto the mail because it thinks it still resides on that server and not externally.  Or better yet is there some procedure that needs to be completed on that X server to delete those emails.  Is this in the recieptients section.

Any Help would be greatly appreciated.

bruceb@mnits.com