After a good friend had a whinge about “mailto:” links in Konsole not opening up in Thunderbird, I checked my install to , and yes when you click an email address in Konsole it launched “kmailservice5” which just sat there consuming CPU cycles and not much else, seemingly without a timeout too.
Its important to note that I have an ArchLinux install , with a “minimal”ish Plasma5 desktop environment.
After much searching (xdg-open xdg-email mimetypes etc), I found the solution.
It is NOT a Plasma5 issue (…Surprise!!…)
The solution (well, my solution) is to start up Thunderbird, click on edit, then preferences, and check that Thunderbird is set to being the default email client… yeah, its that simples, should have looked there much earlier
Hopefully when someone searches for “disable kmailservice5” this post will be of use