Back into testing and checking configuration. This may be more appropriate to the admin thread but I consider this installation as I'm still configuring the system.

Scenario:
We have a pile of aliases and virtual addresses in our current postfix set up. So to make migration to Zimbra easier I was checking the postfix values for alias_maps and virtual_alias_maps. Yes, Zimbra does have the ability to handle this with it's aliases and distribution lists but that will take time to script to get them all in.

So a realistic solution is to use our current postfix alias files.

Issue:

In /var/log/maillog:
Jun 7 05:09:27 localhost postfix/smtpd[31548]: connect from zimbratest.xx.yyy.com[127.0.0.1]
Jun 7 05:09:27 localhost postfix/trivial-rewrite[31541]: warning: do not list domain zimbratest.xx.yyy.com in BOTH mydestination and virtual_mailbox_domains
Jun 7 05:09:27 localhost postfix/smtpd[31548]: DD3F720B04E0: client=zimbratest.xx.yyy.com[127.0.0.1]

So it's taking the machine name as the value for mydomain.

Fix:
Add to main.cf:
mydoman = yyy.com

Questions:
Now, everything seems to work. However:
1. Have I broken something I don't know about?
2. Will these changes need to be redone after any upgrade?

I don't need an answer (although it would be nice) but the dev team may want to think about this. I think if they try setting mydomain in postfix it may help. It won't be right 100% of the time but something like:

echo "mydomain = " `uname -n | awk -F. '{print $(NF-1) "." $NF}' `>>main.cf

would help the config stage of Zimbra's postfix.