A new extra field is now available that allows to extract all email SMTP headers in one go.

SMTP Email headers can now be extracted as an new extra field called Headers
Here is a list of all official (per RFC) header names that can be found in emails:
- Accept-Language
- Alternate-Recipient
- ARC-Authentication-Results
- ARC-Message-Signature
- ARC-Seal
- Archived-At
- Authentication-Results
- Auto-Submitted
- Autoforwarded
- Autosubmitted
- Bcc
- Cc
- Comments
- Content-Identifier
- Content-Return
- Conversion
- Conversion-With-Loss
- Date
- Deferred-Delivery
- Delivery-Date
- Discarded-X400-IPMS-Extensions
- Discarded-X400-MTS-Extensions
- Disclose-Recipients
- Disposition-Notification-Options
- Disposition-Notification-To
- DKIM-Signature
- DL-Expansion-History
- Downgraded-Bcc
- Downgraded-Cc
- Downgraded-Disposition-Notification-To
- Downgraded-Final-Recipient
- Downgraded-From
- Downgraded-In-Reply-To
- Downgraded-Mail-From
- Downgraded-Message-Id
- Downgraded-Original-Recipient
- Downgraded-Rcpt-To
- Downgraded-References
- Downgraded-Reply-To
- Downgraded-Resent-Bcc
- Downgraded-Resent-Cc
- Downgraded-Resent-From
- Downgraded-Resent-Reply-To
- Downgraded-Resent-Sender
- Downgraded-Resent-To
- Downgraded-Return-Path
- Downgraded-Sender
- Downgraded-To
- Encoding
- Encrypted
- Expires
- Expiry-Date
- From
- Generate-Delivery-Report
- Importance
- In-Reply-To
- Incomplete-Copy
- Keywords
- Language
- Latest-Delivery-Time
- List-Archive
- List-Help
- List-ID
- List-Owner
- List-Post
- List-Subscribe
- List-Unsubscribe
- List-Unsubscribe-Post
- Message-Context
- Message-ID
- Message-Type
- MMHS-Acp127-Message-Identifier
- MMHS-Codress-Message-Indicator
- MMHS-Copy-Precedence
- MMHS-Exempted-Address
- MMHS-Extended-Authorisation-Info
- MMHS-Handling-Instructions
- MMHS-Message-Instructions
- MMHS-Message-Type
- MMHS-Originator-PLAD
- MMHS-Originator-Reference
- MMHS-Other-Recipients-Indicator-CC
- MMHS-Other-Recipients-Indicator-To
- MMHS-Primary-Precedence
- MMHS-Subject-Indicator-Codes
- MT-Priority
- Obsoletes
- Organization
- Original-Encoded-Information-Types
- Original-From
- Original-Message-ID
- Original-Recipient
- Original-Subject
- Originator-Return-Address
- PICS-Label
- Prevent-NonDelivery-Report
- Priority
- Received
- Received-SPF
- References
- Reply-By
- Reply-To
- Require-Recipient-Valid-Since
- Resent-Bcc
- Resent-Cc
- Resent-Date
- Resent-From
- Resent-Message-ID
- Resent-Reply-To
- Resent-Sender
- Resent-To
- Return-Path
- Sender
- Sensitivity
- Solicitation
- Subject
- Supersedes
- TLS-Report-Domain
- TLS-Report-Submitter
- TLS-Required
- To
- VBR-Info
- X400-Content-Identifier
- X400-Content-Return
- X400-Content-Type
- X400-MTS-Identifier
- X400-Originator
- X400-Received
- X400-Recipients
- X400-Trace
Custom headers should start with the prefix X- if they are not part of the officially sanctionned headers.