How to encrypt and decrypt GPG mails in the terminal

Encrypting

gpg -e -a -r <receiver@email.address> [-r <receiver2@email.address>]
<type message>
<ctrl d>

Now copy the PGP message to your mail client and send that mail.

• You need one -r flag per receiver address
• With a single receiver, you can also write gpg -ear reci@pie.nt

Decrypting

gpg -d
<paste encrypted message>
<ctrl d>

Adding public keys

gpg --keyserver keyserver.ubuntu.com --search-keys <user@domain.com>
<number of the search result that should be imported>

Also see Using GPG/PGP with Ubuntu and Thunderbird.