On Wed, Nov 04, 2009 at 05:16:33PM +0000, Chris G wrote:
Alternatively if you have a server doing the forwarding then you may have the ability to configure a different port when you configure the domain routing details. That will depend on your setup. I've not tried it, although I keep meaning to check whether the Exim 4 hubbed_host feature can manage it, preferably on a per domain basis.
The router doing NAT is a Draytek Vigor 2820N which can do lots of clever things, I'll have a dig around.
... and aha! :-)
The 2820N allows me to do separate port mapping for the two WANs (one its own ADSL and the other via ethernet to my second ADSL router). So mail sent to my (currently unused for SMTP) BT connection can be port mapped to a different system and/or port number in my LAN.
Excellent, thanks for the pointers and ideas here, it got me searching through the 2820N's facilities.