The other forum thread says the problem goes back to at least 5.0.10. If this is a Microsoft change, then I don't know why it wouldn't go all the way back to 5.0.0.
It is not unprecedented for an out-of-cycle ZCO update to show up on support.zimbra.com, without a corresponding full ZCS release. I'd love to see that happen for 37146, which looks much more urgent (to me) than the other things slated for 5.0.17.
Here's our short-term pickle: There are several things in the 5.0.16 server and webmail that we like, notably
Bug 32536 – Zimbra too trusting of MIME-type sent by client. But the 5.0.16 server's implementation of
Bug 23215 – Eliminate blobs for appointments where possible causes collateral damage on Outlook Connector installs (36534, 35600), essentially requiring us to upgrade all ZCO clients to at least 5.0.16 before upgrading the server.
I don't want to be forced to upgrade everyone's ZCO twice within a couple months. I don't want to wait for 5.0.17 to get all the other goodies in 5.0.16.
I just want to whine, basically.