We have application servers who need to send mail to a pair of web servers, which are behind two 11501. And then the web server will lookup DNS and send the mail to the Internet.
We can ping between application servers and web servers without any problem.
But, we find that, from the application server, we CANNOT send mail to the real ip of the individual web servers. I think the reason is the return IP is changed to vip.
However, with content rules of port 25, from application server, we CAN send mail to the vip (of the two web servers), which CAN then forward the mail to each web server in round robin successfully. The short coming of the setup is the 11501 cannot failover if the smtp deamon of one of the web servers down. That means, smtp (mail service) has no resilience.
Is there any way that we can send mail from the application servers to the real ip of the web servers? In that case, resilience will be retained as UNIX sendmail will check the availability of smtp deamon.