Overview

List members that have Gmail accounts may notice a note as a security warning in the header of received messages/email, stating that the sender "example.com did not encrypt this message".

Gmail's security warning.

Solution

This situation is resolved by configuring Opportunistic TLS (starttls) on the Lyris LM server.

Testing

After implementing the solution described in the article, messages to Gmail list members should be clear of the security warning.