We are using Exim on CPANEL server with CENTOS 5. We have only one mail server hosted on US databasecenter contains all user mailboxes.
Problem is that our users are in two different data centers in US and China. And China datacenter users having difficulties for sending emails along with attachments most of the time because of slow connectivity between US and China datacenters. Because China users have to connect to US DC SMTP server and because of slow connectivity issues users suffers a lot.
At this point, I am trying to achieve functionality like China users will connect to China DC for sending emails I am looking to configure secondary SMTP server on china DC. China SMTP server will then send relay emails to main SMTP server in US DC which will responsible to send emails finally.
Please let me know this will improve email sending from China? How to accomplish this or is there any better solution to resolve this issue?
Currently main mail server which hosts all users mailboxes and I don't want to separate domain name between two datacenters. I still think separate SMTP server on both datacenters can solve email sending issues but how to accomplish this without changing any user email domain e.g. firstname.lastname@example.org or any other idea ?