I did it with a FF plugin called
mailfrom. By default it only has gmail, yahoo and the system, but with a bit of hacking of about:config I got it to open my roundcube webmail.
Once you've installed mailfrom, open a tab and in the address bar write
about:configdo a search for "mailfrom" and you should see a bunch of settings. You need to copy the settings for the existing services, and adapt them for your roundcube setup.
so there's four settings that you need to change
the first is
extensions.mailfrom.servicesJust double click on it and add a name for your webmail service. You can also delete any ones you don't need. The value I set was
default,gmail,roundcubenote the lack of spaces after the commas.
So now you've set up the service, you need to specify a name, a URL and whether it's enabled.
Create a new boolean (right click on the left and choose it from the list) called
extensions.mailfrom.service.roundcube.enabledSet the value of this to
true.
then create a new string. This sets the name that you want to appear to the user. Call it:
extensions.mailfrom.service.roundcube.nameset the value of this to whatever you like, I called mine "roundcube". Creative huh?
then lastly we need to specify the URL. First find the URL of your Roundcube compose page (this is easy, click the compose button in your roundcube page and copy the URL in the page that comes up). To get mailto links to properly supply the values for the
to: and
subject: etc fields you have to add the following to the end of the URL
&_to=$TO&_subject=$SUBJECT&_message=$BODYso it will look like:
http://yourdomain.com/path/to/roundcube/?_task=mail&_action=compose&_to=$TO&_subject=$SUBJECT&_message=$BODYreplace the red bits with the address that you copied from the compose page.
Put that URL in a text editor or whatever so that you can copy it into the next key we create. This is another string and it should be called
extensions.mailfrom.service.roundcube.urlcreate that key, copy over your URL and you're good to go. You might have to restart Firefox. Once you've done that open the preferences for the mailfrom plugin and you should see roundcube in the list of services. select it and hit the default button, and now when you click on a mailto link it will open in roundcube.
HTH
-stib