UPDATED: 2012-02-06 CORRECTION-CORRECTION-CORRECTION!! Major oops in this blog from last year, my apologies if it caused anyone problems! This has also been updated for Zimbra 7.13, as it turns out the Zimbra gui SSL upload is STILL not working for SSL Certificates and returns the same error:
Your certificate was not installed due to the error : system failure: IOException while handling uploaded certificate
So, I revisited my own tutorial and found a couple of errors - corrected version is at the link below.
Hi all, so I thought I would share a simple routine I used this year, that way I can find it next year! Ok, so I was faced with an expiring SSL certificate for my Zimbra Collaboration Suite/Server; ie. mail server, and I HATE digging through documentation every year to figure it out. There was a nice article on installing the original certificate, but nothing on renewing the certificate. Here is the link for the blogpost that worked for me: How to Renew A Godaddy SSL Certificate on Zimbra - WingBlog
I hope that helps someone to NOT have to read the doco.