It's ok, I'll certainly try to explain it as best I can

So, if you opened such a ticket & it was already known or found to be a bug (ie: support/QA can reproduce it on their own boxes) then you get your ticket number reset.
-You can always ask later to get it reset if only you were hitting it at the time & like 2 weeks later everyone sees the issue.
-Which is why many check the forums first or dual post (support ticket & forum thread), we certainly don't mind - it adds to our collective community knowledge
Closer to what you've described above:
-In bugzilla the number of support cases related to those bugs/RFE's are linked/tagged. ie: A RFE with more NE customers requesting that feature gets higher priority.
-Additionally you can open a 'ticket' with simply nothing more than "Please voice my support for
RFE 7473 - Share management and discovery." etc.
-It's a very input oriented process, checkout:
Open Source Product Management: How do features get into Zimbra?
-They're not really just 2 emails per say, you could exchange 40 emails across 2 system down issues if that's what it takes.
-In my personal opinion, two cases where we'll even login remotely to help you out for a ~1k product is pretty darn good.
-You could always purchase another case individually or in discounted groups if it comes to that (think you can get them in 1, 2, & 5 packs).
-And 10 cases for a ~2k+ deployment is far more than you'd get out of most companies - the support reps take it all the way to the engineers if needed.
-They're opened by a phone call, the
support portal, or sending an email to
support@zimbra.com (Don't worry, if someone at your organization were to fire off an email to that address it's always double-checked with you before ticket counts are adjusted).