Email send/receive (pop3/smtp) use only ISP-1

Hello,

I have two ISP connection (ISP-1 and ISP-2) with load balance.
Now I need when my client use email program (outlook, eudora, Thunderbird) then pop3/smtp use only ISP-1 connection.
How to possible it, pl help me

Regards,
Nishadul

ip, firewall, mangle, chain-prerouting, protocol-tcp, dst. port: 25,110, action- mark routing, new routing mark-email

ip, route, at isp-1 connection route, routing mark-email.

remarks: if your mail server is using secure port, you need to put secure port numbers at your dst. port:

Thanks