I am going to try and set up TMDA to work with Zimbra as it will be a MUST if we want to make this move.
Part of the TMDA Instruction states:
MTA Configuration (Postfix)
1. Enable the recipient_delimiter parameter in Postfix's main.cf if it isn't already. Make sure the character you choose matches RECIPIENT_DELIMITER in your ~/.tmda/config.
I cannot find this RECIPIENT_DELIMITER line the the Postfix main.cf.
Can I add it?
Sure. Just be advised we re-write that file on config changes so your changes may get wiped out on restarts or upgrades.