Two exchange servers

[MrOsborne]

I have two domain servers, both running NT4 and both running MS Exchange 5.5. The older one (A) was once PDC. The newer one (B) has since been promoted. I also setup Exch on 'B' and moved most of the mailboxes over. However, 'A' is still the primary Exchange server (if that makes sense). I'm not sure how I switch this over. Is it simply a matter of having our ISP point to 'B'? Is there something I need to do on the servers themselves?

Thanks for any help.

[bAdWaYz]

The MX records will need to be changed to refelect the new server. Also NT4 IMHO is a risk in that setup as its not supported.