I'd seriously consider upgrading to 8.0.6 instead, due to the security vulnerabilities announced the other day and the new vulnerability that was patched in 8.0.6.
As for this issue, the support for 2013 in 8.0.5 is for Outlook 2013 over ActiveSync. I'm not aware of any issues with connecting via IMAP though, so that's the first I've heard of an issue like that one. :(
From: "Tim Ross" <tross@calpoly.edu>
To: "zimbra-hied-admins" <zimbra-hied-admins@sfu.ca>
Sent: Tuesday, December 17, 2013 5:59:56 PM
Subject: Outlook 2013 imap
We are going to upgrade to Zimbra 8.0.5 NE this weekend and in testing on two different machines we ran into problems authenticating to the incoming mail server in Outlook 2013 imap. One machine was windows 8.0 and the other was 8.1. I did find a couple comments out on the forums that other users had run into this problem also. Has anyone else run into this and found a solution/workaround?
We did notice that the 8.0.5 release notes specifically mention that ZCS 8.0.5 supports Outlook 2013 with the ZCO (not just Outlook 2013 in general).
Thanks,
Tim Ross
Application Administrator
Enterprise Applications Group
Cal Poly State University, San Luis Obispo