P-EncryptMail for Outlook allows you to encrypt your Outlook email messages using powerful encryption algorithms (AES, Blowfish, Twofish, TripleDES). You can encrypt an entire mail folder or only selected messages, including attachments. All you have to do to encrypt/decrypt a message is click a button on the newly added toolbar. You can also use the program to send encrypted messages, however the receiver needs to install a free program in order to decrypt the message.

The license of this software is Free Trial Software, the price is $29.95, you can free download and get a free trial.