Moving Exchange and SMTP stops working

We need to replace our Exchange Server 2003 hardware - the system is just not up to the number of accounts we have running on it.

We've built a new server, added it to the domain, promoted it to a controller, installed Exchange and moved the mailboxes - with the old SMTP server/connector still in place, everything works fine.

I've now installed a new SMTP connector, and shut-down the 'old' server and now I can't send or receive internet email - internal mail works fine. So, I guess I have a problem with my connector.

I'm a bit reluctant to delete the old SMTP connector and Exchange server out of Active Directory in hope that it will all start working.

I've worked through the instructions given here http://www.amset.info/exchange/migration.asp but still no luck.

Any suggestions would be gratefully received.

Martin