Can I make links to email addresses open Gmail instead of Evolution?

You might want to take a look at an application called desktop-webmail

It can be installed by clicking on the little icon next to the link or simply by executing following command:

sudo apt-get install desktop-webmail

Then go to "Applications > Internet > Desktop Webmail" and set your web email service. Finally go to "System > Preferences > Preferred Applications" and under "Mail Reader" set Desktop Webmail as your choice.

Desktop webmail supports following services: Gmail, Yahoo, Hotmail and Zoho

This could be a solution for other people as well that use other webmail providers.

Hope it helps :)

Oddly, I couldn't find a simple way to do this in Lucid, so I wrote one:

cat ~/bin/mailto
#!/bin/sh
# mailto: a handler for mailto:[email protected] pseudo-uris

case $1 in
    mailto:*)   addr=`echo $1 | sed 's/^mailto://'` ;;
    *)          addr=$1 ;;
esac

url="https://mail.google.com/mail/?ui=1&view=cm&fs=1&tf=1&to=$addr"

# xdg-open suggestion courtesy of andrewsomething@askubuntu
exec xdg-open $url

Followed by a simple change in System ➤ Preferences ➤ Preferred Applications:

It has worked so well that I forgot I even had to write it until this question was asked.

In Firefox:

Go to Edit -> Preferences -> Applications

Select "mailto" in the "Content Type" list. Select "Use Gmail" in the Action list.