I just thought I'd post this information, since it was a show stopper for me last night when I updgraded to the latest release of zimbra.
First off we have a slightly custom Postfix configuration for use with RT, or Request Tracker. In order to get this working you have to define your mydestinations = $mydomain rather than zimbra's default of localhost in the main.cf. After the upgrade I would add this entry and then after restarting postfix services it would always revert back to localhost no matter what I did.
Long Story short, it appears some changes were made and now the zmscripts that start postfix parse more values than before. The values are parsed out of the following file:
I'm wondering if zomeone from Zimbra can confirm for me if changes to this file will not be overwritten with future upgrades much like the .conf files.