there's comment like "QTextBrowser for some reason insists on putting // in links, this is a crude workaround".

Unfortunately there is no condition for mailto: links, apparently passed by QTextBrowser in the following form:

"mailto:/foo@bar.com"

Thus in the email client, the resulting address is broken: /foo@bar.com (should be foo@bar.com)

The fix:
- add "mailto:" to the list of protocols to fix
- change the regexp to "^([^:]+:)/+", to also support the single '/' after ':'