We have a situation where the AS400 via a dialup internet connection was sending email out. But since we have changed to an ADSL connection and the gateway is no longer the initial dialup server any email we send via the AS400 doesn't go anywhere.
Basic diagram is: "Before"
AS400 <-> Switch Hub <-> Server -> (dialup modem) -> web.
AS400 <-> Switch Hub <-> Server
| - ADSL Modem/Router -> Web.
Because initially the server is the mail handler, it worked. But we believe it know no longer does there but straight out. No matter how we setup the details in TCP and SMTP nothing seems to work.