Message Headers

Last published : Apr 17, 2026
Message headers are custom headers that are used for labeling and sorting messages.
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Note: Filters are not applied to headers generated by these settings.
To configure the section:
  1. Fill in the Header name and Value fields and click +.
  2. Include the full header information either in the message body (with metadata separators in between) or as HTML attachment (as Metadata.HTML attachment).
    Note: These settings do not apply to the EML source.
The existing custom headers can be overridden if the user specifies another Header name. The user cannot specify one of the following headers and the added header must meet RFC 5322 standard:
  • Message-ID
  • From
  • To
  • Cc
  • Bcc
  • Subject
  • Date
  • In-Reply-To
References
  • MIME-Version
  • Content-Type
  • Content-Transfer-Encoding
  • Received
  • Return-Path
  • Authentication-Results
  • DKIM-Signature
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