It works fine. All mail to *@optimalprofit.com goes to the mail server on nt-opro-h0. The problems occur when the mailserver on nt-opro-h0 is down. Exim sends all the mail to smtp.blueyonder.co.uk instead and then it seems to get lost and I never get the mail. I guess it is picking up the blueyonder bit from the following rule in the transport section of the config file.