The good news: Zimbra's mobile support has matured to the point where we have a fairly large number of power mobile users who rarely if ever use the web client. Dedicated ZCO users also fall into this category.
The bad news: These users get no warning that their password is about to expire and subsequently get locked out, generating support calls and ill will.
If you have users who fit in this category, please vote for bug 7812!
Vote early; vote often!