Mgolfieri- Zimbra WebClient As The Default MailTo Handler
From Zimbra :: Wiki
If you want to use the Zimbra webclient as the default email program within your Windows OS, there's a workaround that should work in most cases. In this example, I used Firefox and WinXP, but you can use any other browser/MS OS you prefer, provided that the browser supports CLI arguments when opening URLs. Starting from these instructions from MS:
You should follow them, and once it states that you should set the command lines for outlook, do put the following instead (assuming your firefox is located in the path as in this example):
"C:\Program Files\Mozilla Firefox\firefox.exe" "http://email@example.com&view=compose&to=%1"
You should edit ALL the URL:MailTo in the list to make sure it's being triggered. Just to be sure, please backup the lines you are going to modify in a text file somewhere else. You never know, since as I said this is outside the scope of support, and we should actually wait for this to be implemented:
Once you are done, you should try with any email address that's clickable. The first time you click on a link during a Windows user session it will ask you for the password, and once logged in, you should be good to go. When logging in, check the "remember me" box so that next time you should skip the process of logging in.