Summary
The 5321.MailFrom (Return-Path) and 5322.From are distinct email header fields with different purposes. The 5321.MailFrom, defined in RFC 5321, is used during the SMTP transaction to handle bounces, cannot be the same across ESPs, and is checked by SPF for authentication. The 5322.From, defined in RFC 5322, is the address displayed to the recipient and can be the same across ESPs. DKIM often uses this domain to add a digital signature. DMARC leverages both SPF and DKIM for validation, and inconsistencies between these headers can trigger spam filters and impact deliverability. Their relationship is vital for authentication protocols like SPF and DMARC. Understanding where subdomain.domain.com is located in the headers is important.
Key findings
- SMTP Transaction: 5321.MailFrom is used during the SMTP transaction for bounce handling and is verified by SPF.
- Recipient Display: 5322.From is the sender address displayed to the recipient and is often used for DKIM signing.
- ESP Uniqueness: The 5321.MailFrom cannot be the same across different ESPs.
- Authentication Impact: The relationship between 5321.MailFrom and 5322.From is crucial for SPF, DKIM, and DMARC authentication.
- Deliverability Risk: Inconsistencies between 5321.MailFrom and 5322.From can trigger spam filters and reduce deliverability.
Key considerations
- Authentication Protocols: Implement SPF, DKIM, and DMARC correctly to ensure proper authentication.
- Header Consistency: Maintain consistency between the domains used in 5321.MailFrom and 5322.From to improve deliverability and prevent spoofing.
- DMARC Alignment: Ensure proper alignment between SPF and DKIM to pass DMARC validation and protect your domain reputation.
What email marketers say
7 marketer opinions
The 5321.MailFrom (Return-Path) and 5322.From are distinct email header fields with different roles. The 5321.MailFrom, part of the SMTP envelope, is used for technical transport and bounce handling. SPF authenticates the 5321.MailFrom domain. The 5322.From is the sender address displayed to the recipient and is often used for DKIM signing. Differences between the domains can trigger spam filters, making consistency and proper SPF, DKIM, and DMARC authentication crucial for deliverability.
Key opinions
- Bounce Handling: 5321.MailFrom (Return-Path) is used for handling bounce messages.
- Recipient Display: 5322.From is the address displayed to the recipient.
- SPF Authentication: SPF authenticates the domain in the 5321.MailFrom field.
- DKIM Signing: DKIM often uses the 5322.From domain to add a digital signature.
- Deliverability Impact: Inconsistencies between 5321.MailFrom and 5322.From can negatively impact email deliverability.
Key considerations
- Consistency: Maintain consistency between the domains used in 5321.MailFrom and 5322.From to avoid triggering spam filters.
- Authentication: Implement SPF, DKIM, and DMARC to properly authenticate your emails and improve deliverability.
- Domain Alignment: Ensure proper alignment between the domains used in SPF and DKIM to pass DMARC validation.
Marketer view
Email marketer from StackOverflow shares that 5321.MailFrom is part of the SMTP envelope (the technical information used for email transport), and 5322.From is part of the email's headers (what the user sees).
15 May 2022 - StackOverflow
Marketer view
Email marketer from Mailgun shares that the 5321.MailFrom (Return-Path) is used for handling bounces, while the 5322.From is what the recipient sees in their email client. They can be different, but discrepancies can affect deliverability.
21 May 2025 - Mailgun
What the experts say
3 expert opinions
The 5321.MailFrom and 5322.From are distinct email header fields with different purposes. The 5321.MailFrom is used during the SMTP transaction to handle bounces. It cannot be the same across different ESPs. The 5322.From is the address displayed to the recipient and can be the same across different ESPs. Their relationship is vital for authentication protocols like SPF and DMARC; discrepancies can lead to deliverability issues.
Key opinions
- SMTP Transaction: 5321.MailFrom is used during the SMTP transaction.
- Bounce Handling: 5321.MailFrom determines where bounce messages are sent.
- Recipient Display: 5322.From is the address displayed in the recipient's email client.
- Authentication Impact: The relationship between 5321.MailFrom and 5322.From is vital for authentication (SPF, DKIM, DMARC).
- ESP uniqueness: 5321.from can not be the same across different ESP's
Key considerations
- Authentication: Ensure proper alignment and authentication using SPF and DMARC.
- Deliverability: Address discrepancies between 5321.MailFrom and 5322.From to avoid deliverability problems.
Expert view
Expert from Email Geeks explains to understand email headers we need to know where subdomain.domain.com is located. The 5322.from can be the same at different ESPs but the 5321.from cannot. The d= value can be the same at different ESPs.
1 May 2023 - Email Geeks
Expert view
Expert from Word to the Wise explains that the relationship between 5321.MailFrom and 5322.From is vital for authentication protocols like SPF and DMARC. Discrepancies can lead to deliverability problems.
26 Mar 2024 - Wordtothewise.com
What the documentation says
3 technical articles
The 5321.MailFrom (Return-Path) and 5322.From email headers serve different roles according to RFC specifications and DMARC standards. 5321.MailFrom is used during the SMTP transaction, specifying where bounce messages are sent and is critical for delivery. SPF checks this domain. 5322.From is the 'From:' header displayed to the recipient, part of the message body, and not used for routing. DKIM often uses this domain. DMARC leverages SPF and DKIM to validate email sources, using alignment policies to determine how to handle authentication failures.
Key findings
- SMTP Delivery: 5321.MailFrom is used during the SMTP transaction for bounce handling and delivery.
- Recipient Display: 5322.From is the address displayed to the email recipient.
- SPF Validation: SPF checks the 5321.MailFrom domain.
- DKIM Signing: DKIM often uses the 5322.From domain.
- DMARC Validation: DMARC uses SPF and DKIM alignment to validate email sources.
Key considerations
- Authentication Setup: Properly configure SPF and DKIM to ensure email authentication success.
- DMARC Policies: Implement DMARC policies to handle messages that fail authentication checks.
Technical article
Documentation from RFC Editor explains that the 5322.From header is the 'From:' header field that email clients display to show the author(s) of the message. It's part of the message body and is for display purposes, not used by the SMTP server for routing.
30 Sep 2024 - RFC Editor
Technical article
Documentation from RFC Editor explains that the 5321.MailFrom (or Return-Path) is used during the SMTP transaction. It specifies where bounce messages should be sent. It's crucial for the actual delivery process and is used by servers to handle bounces.
28 Jul 2023 - RFC Editor
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