Enable TLS encryption with no backup method

In the Email Security module, if you select only TLS for message encryption and the client and server cannot negotiate a secure TLS connection, the message is sent to a delayed message queue for a later delivery attempt.

Steps

  1. Navigate to the page Settings > Inbound/Outbound > Encryption.
  2. From the pull-down menu Encryption method, select Transport Layer Security (TLS).
  3. Use only TLS for message encryption; from TLS Encryption Backup Options, select Use TLS only (no backup encryption method; message is queued for later delivery attempt).
  4. Click OK.
    The settings are saved.