Exchange mail server authentication problem
We're currently in the process of transferring our broadband supplier from the company which provides our email to BT infinity. When we switch the cabling over, we are disconnected from external emails - incoming ones queue up, and outgoing ones give a "550 relay not permitted" error when they bounce back. Internet connection works fine on the new system, so that's not the problem.
Obviously this must be to do with mail server authentication - as it works fine when we go back to the email provider's connection. However, the details in the mail server have been rolled over from at least two previous setups and I have no idea where the authentication information needs to go. Where would I look to input the details, as I've found various places. The fact we've been using this company since 1998 and they won't co-operate with the migration isn't really helping matters...
Any help gratefully received, as the kids come back on Thursday and we need it transferred before that if possible.