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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 I cant make the (A) entry of 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!


Some clients have their mail point to instead of 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

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up vote 1 down vote accepted

Ultimately, you need to get the customer configurations cleaned up, or it will bite when you next want to switch hosts.

Run a mail-server on which forwards mails onto the correct server. Use the logs from that server in daily batch processing to determine which customers are misconfigured. Generate notices to the customers.

Bonus points for having a clause in your contract which allows you to charge more money if the customers are misconfigured and causing you operational expense. :)

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Thanks for the answer, i will most likely try something amongst these lines – Dexirian Oct 31 '13 at 15:43

Could you use socat to forward connections for your clients from to

So on you would run:

    socat TCP-LISTEN:25,fork
    socat TCP-LISTEN:110,fork
    socat TCP-LISTEN:993,fork
    socat TCP-LISTEN:995,fork

for all the services you want to pass through. That way you don't even need to run a mailserver on

Extracting the usernames to see who needs updating will require more information about what services they are using. You could sniff them if it's unencrypted, or terminate the SSL using stunnel to get access to it. Your SMTP/POP3/IMAP server logs should also be useful here.

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