I've been working on this issue for some time now and just can't seem to figure out where I'm going wrong. I'm trying to get Internet Explorer 8 to trust the certificate presented by Zimbra in the ZWC but no matter what I try, I just can't get a trusted connection. All my users are getting the warning page in IE8 and have to click on 'continue to this page' link to get to the Zimbra login page. This page also appears sometimes when they're working within Zimbra -- eg. opening PDF attachments -- and is interrupting to say the least.

I have tried importing the certificate into various places including the 'Trusted Root Certification Authorities' store as is recommended in various places and it makes no difference. I double-checked that the certificates were in fact imported into these stores using the Certificates MMC console. I've made sure that the domain for the zimbra host matches the certificate. The workstations are running XP SP3 with latest IE8, but I also had this problem on IE7 before upgrading.

Any help with this would be greatly appreciated. Thank you.