I have two network cards, the SMTP sends from working network card

I have two network cards in my server, and both of them are connected, one is connected local and other one internet,

I have crea开发者_运维问答ted a SMTP service, the problem is that the smtp only tries sending emails from the local network card.

I want it to try send emails from the internet network card, how can this be solved?

SMTP does not know about network interface cards. The decisions is made by the operation system. What does your routing table look like, e.g. the output of "netstat -rn" on a Unix-like OS, and what is the IP address of the destination that your SMTP service tries to connect to?