Try
Noroom's Listmanager.
If the contacts are still to be found in any list..blocklist, allowlist, reverselist then you will be able to add them back easily
P.S. It is not wise to use MSN Messenger for business, it's not designed for it and surely at this moment far from stable enough. I suggest you use Windows Messenger (Supported Operating Systems: Windows 2000 Service Pack 4; Windows Server 2003; Windows Server 2003 Service Pack 1; Windows XP 64-bit; Windows XP Service Pack 1; Windows XP Service Pack 2; Windows XP Tablet PC Edition) for business instead (wich was designed for business).
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