Why does PGP Desktop automatically attempt to encrypt all email messages and searches for recipients keys? Is it possible to encrypt email messages to only specific recipients?
By default, PGP Desktop uses Opportunistic Encryption for accounts added as a PGP Messaging Service. Oopportunistic Encryption means that, if PGP Desktop has the recipient's verified public key it automatically encrypts the message. Otherwise, it sends the message in clear text (unencrypted).
Each time an email message is sent, PGP Desktop searches the local keyrings as well as any keyservers in the PGP Keyservers List for the recipients key.
You can configure PGP Desktop to only encrypt to recipients you specify by disabling Opportunistic Encryption policy.
To disable Opportunistic Encryption:
Open PGP Desktop.
Click the PGP Messaging Control box and then select your email account name.
Under Security Policies, click the Edit Policies button.
Remove the checkmark next to Opportunistic Encryption (default) and click Done.
To encrypt email messages to a specific recipient you can use [PGP] in the subject line or use the Encrypt and Sign buttons in versions of PGP Desktop 10.x.