You can use kmail and gpg to send encrypted or digitally signed mail. To do this, there are the buttons "sign" and "encrypt" in the kmail compose window. It appears if you click on "File|New|New message".

How to...

Import a saved keyring

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 your private key to ultimate.

TroubleShooting

Whatever problems arise, first make sure your gpg is properly set up:

List your keys

gpg --list-keys

Has to deliver something like a sensible list of keys.

Check the output of

gpg --update-trustdb

In case of a problem look at the below.

no ultimately trusted keys found

If

gpg --update-trustdb

delivers

gpg: no ultimately trusted keys found

Call kgpg and set the trust of your private key to ultimate.