The problem is that /usr/share/applications/claws-mail.desktop is missing mimetype.
The workaround is: 1. add MimeType=x-scheme-handler/mailto; into /usr/share/applications/claws-mail.desktop 2. run update-desktop-database
The problem is that /usr/share/ applications/ claws-mail. desktop is missing mimetype.
The workaround is: x-scheme- handler/ mailto; applications/ claws-mail. desktop desktop- database
1. add MimeType=
into /usr/share/
2. run update-