Been trying to find a solution to this for a while without success so here i go :

I was given the task to build a High-Availability Load-Balanced Network Cluster for our 2 linux servers. I did some workaround and managed to get a DNS + SQL + Web Folders + Mails synchronisation going between both. Now i would like my server 2 to only do mailing and server 1 to only do web hosting. I transfered all the accounts for 1 to 2 using the WHM built-in account transfert feature. I created 2 different rsync jobs that sync, update, and delete the files for mail and websites.

Now i was able to successfully transfer 1 mail accounts from 1 to 2, and the server 2 works flawlessly. All i had to do was change the MX entries to point to the new server and bingo. Now my problem is, some clients have their mail softwares configured so that they point to oldserver.domain.com. I cant make the (A) entry of oldserver.domain.com point to the new server for obvious reasons. I thought of using .foward files and add them to the home directories of the concerned users but that would be very difficult.

So my question is : Is there a way to configure exim so that it will only foward mails to the new server? I need to change all the users so they use their mail on server 2 without them doing anything. Thanks!

EDIT : TO CLARIFY MY PROBLEM

Some clients have their mail point to oldserver.xyz instead of mail.olderserver.xyz I want to know if i can do something to prevent modifying the clients configuration

I would also like to know is there is a way to find out what clients aren't properly configured