First, Zimbra rocks and we're very happy to be 95% of the way there in our Exchange to Zimbra migration!
We have an annoying issue though that affects our T-bird/Lightning users who have aliases. Instead of using the actual email address of the user's account as the organizer of events, an alias is used. Based on our tests it appears that T-bird/Lightning is choosing the email address to use based on alpabetical order of the domain name(s) of the primary address and any aliases that a user has.
If a user had the following aliases and primary email address then Lightning would choose email@example.com even though the user's actual email address is firstname.lastname@example.org.
Mailbox Address: email@example.com
Alias 1: firstname.lastname@example.org
Alias 2: email@example.com
I know this isn't a support site for Lightning but I'm hoping maybe someone can help here because we'd either like to choose which email address we're sending as the meeting/event organizer or have it default to the actual email address on a mailbox, not any aliases that might be present. When our users setup their CalDav calendar in Lightning they choose their actual email address during the New Calendar Wizard, so that setting doesn't seem to affect which email address is used as the event organizer.