The RMail encryption service uses Transport Layer Security (TLS) as a default for sending and receiving encrypted emails. TLS is a secure “tunnel” protecting the message from the edge of the sender’s network to the edge of the recipient’s network. When an encrypted message is sent via TLS, it will be decrypted at the server level, and therefore does not require the recipient to input a password to access it.

TLS is enabled by default on our Control Panel for a customer’s account, so messages are always sent securely to RPost. We then use our TLS detection service to determine if the recipient's mail server has TLS enabled:
- If TLS is detected, emails are  delivered using Transmission, securely all the way to the mail server. The message is decrypted at the mail server and is sent to the recipient's mailbox unencrypted with no password requirement. The message is marked with the RPost banner and is clearly identified as being “transmitted encrypted”.

- If TLS is not detected, emails are sent using Message Level Encryption. Encrypted messages sent by Message Level Encryption provide privacy by wrapping the email and attachments inside a password protected AES 256-bit encrypted PDF. Emails require a decryption password to open and view the message body and attachments.

To learn more refer to article RMail Encryption.