KMail/gpg

You can use gpg to send encrypted or digitally signed mail.

First make sure your gpg is properly set up:

gpg --list-keys

Check that

gpg --update-trustdb

does not deliver

gpg: no ultimately trusted keys found

If you have a keyring saved to your disk, reload ("import") it like this:

cat secring.skr | gpg --import

Then call kgpg and set your trust on this key to ultimate.