Skip to content

header-rules.md

Latest commit

 

History

History
144 lines (109 loc) · 2.85 KB

header-rules.md

File metadata and controls

144 lines (109 loc) · 2.85 KB
Raw

Header Rules Guide

Sendry supports header manipulation rules to modify email headers before sending. This is useful for:

  • Removing headers that expose internal infrastructure
  • Adding custom tracking or compliance headers
  • Standardizing headers across all outgoing mail

Configuration

Header rules are configured in the header_rules section of the config file. No additional setup is required.

header_rules:
  # Global rules (applied to all domains)
  global:
    - action: remove
      headers:
        - "X-Originating-IP"
        - "X-Mailer"
        - "User-Agent"
    - action: add
      header: "X-Processed-By"
      value: "Sendry"

  # Per-domain rules
  domains:
    example.com:
      - action: replace
        header: "X-Mailer"
        value: "Example Mail Server"

Actions

Remove

Removes specified headers from the email.

- action: remove
  headers:
    - "X-Originating-IP"
    - "X-Mailer"
    - "User-Agent"

Header names are case-insensitive. All occurrences of the specified headers are removed.

Replace

Replaces the value of a header. If the header doesn't exist, it's added.

- action: replace
  header: "X-Mailer"
  value: "MyMailServer/1.0"

Only the first occurrence is replaced if multiple headers with the same name exist.

Add

Adds a new header. Always appends, even if the header already exists.

- action: add
  header: "X-Processed-By"
  value: "Sendry"

Rule Order

  1. Global rules are applied first
  2. Domain-specific rules are applied after global rules
  3. Rules are applied in the order they appear in the config

Common Use Cases

Privacy Protection

Remove headers that reveal internal infrastructure:

header_rules:
  global:
    - action: remove
      headers:
        - "X-Originating-IP"
        - "X-Mailer"
        - "User-Agent"
        - "X-MimeOLE"

Compliance Headers

Add required compliance or tracking headers:

header_rules:
  global:
    - action: add
      header: "X-Organization"
      value: "Example Corp"
    - action: add
      header: "X-Compliance-ID"
      value: "GDPR-2024"

Per-Domain Branding

Different headers for different sending domains:

header_rules:
  domains:
    marketing.example.com:
      - action: add
        header: "X-Campaign-Source"
        value: "marketing"
    support.example.com:
      - action: add
        header: "X-Department"
        value: "support"

Replace Default Headers

Replace auto-generated headers with custom values:

header_rules:
  global:
    - action: replace
      header: "X-Mailer"
      value: "Sendry MTA"

Notes

  • Header matching is case-insensitive (X-Mailer matches x-mailer, X-MAILER)
  • Multiline headers (with continuation) are handled correctly
  • Rules do not affect the message body
  • DKIM signing happens after header rules are applied