Now I have 2 email servers with different ip addresses that currently point to themselves. one is my.account.com (currently being used) and the other is zimbra.my.account.com (Intended to be a primary MX).
In the zimbra.my.account.com, I have created a domain "@my.account.com" similar to my old email server. I have added all accounts in my old email server (email@example.com,...,etc.) to my new email server zimbra.my.account.com (firstname.lastname@example.org,...,etc.). in my new email server, I have set it up to relay emails to other users still on the current email server (smtp:my.account.com:25). I have set the MX record priority to "5 zimbra.my.account.com" (primary) and "10 my.account.com" (secondary).
Now I want to start migrating accounts from the old email server (my.account.com) to the new email server (zimbra.my.account.com) one at a time:
First, accounts in the old email server cannot receive most emails coming from outside: NO QUEUE REJECT RCPT FROM ......., but some of the mails are coming from a legit domain and host
Second, accounts in the old email server my.account.com cannot send mail to already migrated accounts in zimbra.my.account.com (email@example.com), instead it relay it to the local account (itself).
Finally, when already migrated accounts try to send email to accounts that still reside on the old email server it loops back to itself even though I have not made it known to the new email server that the accounts now receive emails on it (....lmtp:7025)
How do I make it known to postfix that the account that resides in my old server now receives email in the other server. So users in the old server send mail to users that have been migrated to the new server zimbra.my.account.com instead of to the local server itself (my.account.com).
this is a Primary and Secondary MX scenario where some users in the secondary stays in the scondary but still receive emails from everywhere and vice versa