Summary
Emails bouncing with RFC 5322 compliance errors when sent to Gmail corporate addresses often result from a complex interplay of factors. The most prominent issue is related to the proper formatting and existence of the 'From' header, but other critical aspects include adherence to the Internet Message Format standard as defined in RFC 5322, proper configuration of email servers (such as Exchange Server or Amazon SES), authentication (SPF, DKIM, DMARC), and avoiding spam triggers. Additional points of failure encompass issues with MIME structure, invalid characters in headers or body, improper HTML coding, header folding, IPv6 configuration, and the presence of a properly implemented List-Unsubscribe header. Content that triggers spam filters can also lead to rejections, even when the basic email format complies with RFC 5322.
Key findings
- Missing/Incorrect 'From' Header: The 'From' header must be present, correctly formatted, and valid.
- RFC 5322 Non-Compliance: Emails must adhere to the Internet Message Format standard as defined in RFC 5322.
- Server Configuration Issues: Incorrect settings in Exchange Server, SES, or other email servers lead to compliance errors.
- Lack of Authentication: Failure to implement SPF, DKIM, and DMARC records results in deliverability problems.
- Spam Triggers: Spam filters are highly sensitive; avoid URL shorteners, excessive exclamation points, and other common spam triggers.
- IPv6 Related Configuration: If sending over IPv6 ensure that full circle rDNS is set up.
Key considerations
- Validate 'From' Header: Double-check the 'From' header for presence, correct formatting, and a valid domain.
- Review Email Structure: Ensure the overall email structure complies with RFC 5322 specifications.
- Check Server Settings: Verify and correct SMTP settings in Exchange Server, SES, or other email servers.
- Implement Email Authentication: Set up SPF, DKIM, and DMARC records to authenticate your emails.
- Audit Email Content: Review email content for spam triggers, invalid characters, and other potentially problematic elements.
- Verify PTR record settings: Verify there is a PTR record configured
- Check MIME configuration: Verify that MIME is set up correctly.
- List Unsubscribe Header: Verify there is a List Unsubscribe Header configured.
What email marketers say
9 marketer opinions
Emails to Gmail corporate addresses bouncing with RFC 5322 compliance errors often stem from issues with email formatting, headers, authentication, or content. Missing or incorrectly formatted 'From' headers, MIME structure problems, and invalid characters are common culprits. Improper HTML coding, header folding issues, and the inclusion of spam triggers can also lead to errors. Implementing SPF, DKIM, and DMARC records for email authentication is crucial, as is configuring a PTR record. Clean code, adherence to email standards, and avoiding spammy content are also essential for improving deliverability.
Key opinions
- Missing/Invalid 'From' Header: The 'From' header is mandatory; ensure it's present and correctly formatted.
- MIME and Header Issues: Problems with the email's MIME structure or invalid characters in headers can cause errors.
- Spam Triggers: Spam filters are sophisticated; avoid URL shorteners, excessive exclamation points, and spammy keywords.
- Authentication: SPF, DKIM, and DMARC are vital for email authentication and improving deliverability.
- HTML Coding: Improper HTML coding in the email's body can trigger RFC 5322 errors.
Key considerations
- Address Formatting: Double check that your addresses are formatted correctly and exist.
- Reviewing Content: Review email content and links to ensure they are not triggering spam filters.
- Configure PTR Record: Configure PTR records correctly, to verify your server's identity.
- Addressing Headers: Check your email headers for RFC 5322 compliance.
- Implement SPF, DKIM, DMARC: Set up email authentication to improve deliverability.
Marketer view
Email marketer from Mailjet explains that RFC compliance errors can occur if the email's 'From' header is missing or incorrectly formatted, if there are issues with the message's MIME structure, or if the email contains invalid characters or formatting in the headers.
1 Aug 2021 - Mailjet
Marketer view
Email marketer from Stack Overflow responds that missing 'From:' header may cause this error, it is required. You can set it with `$headers .= "From: info@example.com";`.
3 Oct 2023 - Stack Overflow
What the experts say
9 expert opinions
Emails bouncing with RFC 5322 compliance errors in Gmail corporate addresses often result from a combination of missing or incorrectly formatted email headers (especially the 'From' header), EHLO configuration issues, and content-related problems like unusual links or improper header folding. Additional factors include not meeting IPv6 requirements, absence of a Message-ID, and incorrect 'From' address formatting. Failure to implement a valid List-Unsubscribe header may also increase spam complaints, indirectly impacting deliverability.
Key opinions
- Missing From Header: A missing 'From' header is a primary cause of RFC 5322 errors.
- Improper Header Formatting: Incorrectly formatted or folded headers contribute to compliance issues.
- Unusual Email Content: Unusual or potentially malicious links can trigger RFC 5322 related blocks.
- IPv6 Configuration: Sending over IPv6 requires specific configurations, including full circle rDNS.
- From Address Issues: Correct formatting of 'From' address is important.
Key considerations
- Check From Header: Ensure the 'From' header is present and adheres to RFC 5322 standards.
- Verify EHLO Configuration: Configure the EHLO with a fully qualified domain name.
- Review Content: Evaluate the content for any potentially problematic links or non-ASCII characters.
- Configure IPv6 Settings: If using IPv6, implement full circle rDNS and verify AAAA records.
- Implement List-Unsubscribe: Add or Correct List-Unsubscribe Header.
Expert view
Expert from Email Geeks mentions the absence of a Message-ID which is not ideal, but shouldn't cause the error. A reasonable smarthost should add a Message-ID if needed.
24 Dec 2023 - Email Geeks
Expert view
Expert from Spamresource explains that the 'From' address needs to be formatted correctly and exist. It must not contain invalid characters, and the domain part of the address must resolve to a valid DNS record. Check that the email is using a valid return-path and that there are no encoding issues with the address.
30 Dec 2023 - Spamresource
What the documentation says
5 technical articles
RFC 5322 compliance errors when sending emails to Gmail corporate addresses arise primarily from failing to adhere to the Internet Message Format standard. Official documentation from Google, the RFC Editor, Microsoft, IETF, and Amazon Web Services all emphasize the critical importance of the 'From' header and overall email structure adhering to RFC specifications. Incorrect server settings (e.g., in Exchange Server or SES), authentication issues, and deviation from email standards lead to delivery problems.
Key findings
- RFC Standard: Non-compliance with RFC 5322 is the root cause.
- Mandatory From Header: The 'From' header's presence and correct format are crucial.
- Server Configuration: Incorrect settings in Exchange Server or SES can trigger the errors.
- Email Structure: Overall email structure and syntax must comply with the Internet Message Format.
- Authentication: Sender Verification is very important in this context.
Key considerations
- Adhere to RFC Standards: Ensure emails fully comply with RFC 5322 and related standards.
- Verify From Header: Carefully check the 'From' header's formatting and presence.
- Configure Server Settings: Review and correct SMTP settings within Exchange Server or SES.
- Ensure Authentication: Use robust email authentication methods (SPF, DKIM, DMARC) in SES.
- Check Sender Verification: Make sure to configure sender verification settings correctly.
Technical article
Documentation from Google Workspace Admin Help explains that RFC 5322 compliance errors arise when emails don't adhere to the Internet Message Format standard, specifically the 'From' header, which must be present and correctly formatted to ensure proper email delivery to Gmail.
15 Jun 2022 - Google Workspace Admin Help
Technical article
Documentation from Microsoft Support details that incorrect or missing settings within Microsoft Exchange Server can lead to RFC 5322 compliance issues. Ensure that the 'From' header is properly configured and that the server's SMTP settings adhere to email standards to avoid bounces.
24 Aug 2024 - Microsoft Support
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