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As of March 1, 2022, the legacy Barracuda Essentials Security, Compliance, and Complete editions are no longer available for purchase. Only existing customers can renew or add users to these plans. The documentation related to these plans will no longer be available after October 30, 2022. For more information on the latest Email Protection plans, see Barracuda Email Protection.

To update your bookmarks, see the following for the latest documentation:

Note that MSP customers should continue to follow Barracuda Essentials for MSPs.

Understanding the Message Header and Envelope

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The Barracuda Email Security Service (ESS) is a pass-through service, accepting connections from a mail server, getting the initial RCPT TO line and connecting to the destination mail server. To understand how mail is delivered, an email message has two TO addresses, a HEADER TO address and an ENVELOPE TO (RCPT TO) address. The HEADER TO is read by users and mail clients but is not used for mail delivery. The ENVELOPE TO is used by mail servers to determine where the mail is being delivered. In the ESS Message Log, click the Show Details link in the message header for HEADER TO and ENVELOPE TO details.

In the below example:

  • The HEADER TO information in the red box shows the email address ( to deliver the mail to. This is not used for the delivery of the message.
  • The green box is the information created by ESS when the mail is accepted and processed. This can be used to track messages in ESS.
  • The ENVELOPE TO (RCPT TO) information in the blue box shows the email address ( given by the sending mail server. This is used to deliver the mail and shows the details about the delivery of the message.


Note: When the ENVELOPE TO information does not match the HEADER TO/CC information, it is usually because the sender did not include or removed email addresses in the reply message. The header information remains the same in the reply, but the mail is only delivered to the ENVELOPE TO set by the mail server.

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