This can occur depending on the settings defined in the Security Policies
for the PGP Messaging service. This happens when the policy Opportunistic Encryption
within the PGP Messaging service is configured to Block message
when a recipient's key is not available.
PGP Desktop checks only the default keyring. To send encrypted email to a recipient whose key is on your local keyring, be sure to import the key to your default keyring. If you have multiple keyrings, the default keyring is the first keyring listed in the PGP Keys control box. To specify a different default keyring, right-click the keyring in the PGP Keys control box, choose Properties, and select the Default Keyring checkbox.
To edit the Opportunistic Encryption policy
- Open PGP Desktop.
- Click the PGP Messaging Control box.
- Select your account name under PGP Messaging.
- In the Security Policies section, click Edit Policies.
- Select Opportunistic Encryption (default) then click Edit Policy.
- If the setting for when the recipient's key is not available is set to Block message, change the setting by clicking the down arrow to use Send message unsecured or Clear-sign message.
- Click OK to update the settings then click Done.