I am forced to urgently move exim mail server to different server. Exim4 was installed on old server with lots of different other services. So, now I want to devide services without making any changes in DNS. I want to somehow divide on router mail traffic from other trafic and then route mail trafic to another IP. What is the best way to do so for exim4? Can it be done by TCP or UDP port redirection? If so - what ports need to be redirected to another IP so that exim4 mail will work? May be it is still better to use DNS and it is more efficient to change MX records?