Until communication between xdg-email and claws-mail is fixed in Ubuntu LTS, I've resolved the problem by (a) adding a claws-mail line in the apparmor profile for senddoc and reloading the policy. and (b) setting Tools/Options/Internet/Email to specify /usr/bin/claws-mail.
I don't like messing with system files like that, but it now works again properly.
Until communication between xdg-email and claws-mail is fixed in Ubuntu LTS, I've resolved the problem by (a) adding a claws-mail line in the apparmor profile for senddoc and reloading the policy. and (b) setting Tools/Options/ Internet/ Email to specify /usr/bin/ claws-mail.
I don't like messing with system files like that, but it now works again properly.