Thank you for this. Yes it did help my issue and now I'm able to accept on Zimbra and on the BlackBerry. There is still a strange issue though. When I send an invite to a meeting and they accept on Zimbra web client then the Inviter sees that they accepted, but on the user who accepted (the webmail zimbra client) their calendar sees this as tentative. I can hit accept again, it still shows as tentative. It also shows as tentative in the BlackBerry. Again it shows on the Invitee's calendar that they had accepted though.
The other part of this is if I accept the invite from the BlackBerry, it shows up both calendars as accepted, but when it alerts the Inviter of acceptance, the inviter's calendar shows the user as in need of action but it shows under accepted users with firstname.lastname@example.org has accepted. It is doing this for all who accept from a BlackBerry. I'm guessing when the BB sends out the acceptance message it is putting in this comx suffix. comx is definitely not supposed to be there as the real email is email@example.com and I think this is could be causing why it doesn't report properly when the blackberry accepts. Any thoughts on how to resolve these two? Thanks.