To reproduce: In KGgp: 1. Click "Export Public Key" 2. Select "Email" 3. Click "OK" This opens a new KMail window for composing an email. However, the email is empty. I would expect the public key to be attached to the email. Tested on Fedora 28 KDE Spin.
This is a KMail problem. If you use a different email client it works. *** This bug has been marked as a duplicate of bug 332368 ***