Mail - dnschneid/crouton GitHub Wiki
I installed vanilla Ubuntu, and added latest Thunderbird, but did not find way to make it default mail client
it is very irritating when once one has in error clicked on a mail link in browser, and kmail is not installed, it seems not to be possible to close, and one is stuck with endless bouncing ball.
#354151 New: kmailservice5 restart repeatly when no mail client is installed