Zivver messages that you sent with Zivver Plugin Assisted Mail Submission (PAMS) or Zivver OWA Assisted Mail Submission (OWA-AMS) enabled in the Zivver client carries these artifacts.

• The custom mail header zivver-relay with value zivver-message-info.
• A hidden metadata file.

Every outbound message with the zivver-relay mail header must be submitted to the Zivver SMTP Gateway.

It depends on your mail server or secure email gateway (SEG) whether and how you can filter on that mail header. Next, your server or SEG must submit this filtered out message to the Zivver SMTP Gateway.