@scottalanmiller - Do you have the paid supported version of Zimbra? and how are you syncing with mobiles/tablets, you using striaght imap or activesync
Just using IMAP. NTG used to be a commercial Zimbra hoster, no need for us to pay for support :) We do use it on mobile, but IMAP works great for mobile.
I'm currently using it with Nylas Mail on my Korora desktop, but mostly because I'm using that for my Office 365 mail, too.