A PGP encrypted email doesn't get "decrypted" when it's being transferred. That's the whole purpose of PGP encryption, to encrypt it before it even gets transferred or stored, which is what we do. If you set up a PGP key, use WKD, then your emails will be stored as encrypted (not only is your database encrypted with your password, but the emails themselves can be PGP encrypted this way), and any sender attempting to send to you will automatically have their message PGP encrypted to you, if it is not already (in case their mail client doesn't use WKD).