Aaron Wolfe wrote:
This doesn't prove Postfiix is using the wrong interface. It simply means the traffic is seen by the upstream server as coming from the wrong interface. It is much more likely that your NAT config is wrong and is SNATing the mail traffic to the same address that it SNATs everything else.
You were 100% right - the iptables setting had incorrectly left out the private source address, and was SNATing the public traffic when it wasn't supposed to. Telling the SNAT to only touch 192.168.0.0/16 solved the problem.
As I said before, thank you for the help. Regards, Graham --
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