How to format messages according to RFC 5322 for Gmail sender guidelines?

Key findings

• Core standard: RFC 5322 specifies the Internet Message Format, covering headers like From, To, Subject, Date, and the message body.
• Gmail's emphasis: Gmail's sender guidelines explicitly require messages to be formatted according to RFC 5322, particularly highlighting the need for a valid Message-ID.
• Line length: Emails should adhere to a maximum line length of 998 characters, including the Carriage Return (CR) and Line Feed (LF) characters.
• Header integrity: Avoid duplicating standard headers like To:, From:, or Subject:, as this can cause parsing issues.

Key considerations

• ESP responsibility: For most senders, the ESP (Email Service Provider) should automatically ensure RFC 5322 compliance. If formatting errors occur, it's typically a bug on the ESP's end.
• Deliverability impact: While compliance is required, direct RFC 5322 formatting issues are rarely the primary cause of poor deliverability. Factors like sender reputation, content quality, and address acquisition practices are more common culprits.
• Troubleshooting bounces: If you experience bounces specifically citing RFC 5322 errors, it's crucial to investigate your email headers and potentially consult with your ESP.
• HTML and line breaks: HTML tags for line breaks do not count towards the RFC 5322 line length limit. Actual physical line breaks (CR/LF) are necessary to ensure compliance.

Key opinions

• ESP responsibility: Marketers largely believe that their Email Service Providers are responsible for ensuring email formatting adheres to RFC 5322 standards.
• Focus on content: Their primary concern remains email content, audience engagement, and overall campaign performance, not low-level technical formatting.
• Minimal direct impact: Unless their ESP notifies them of specific formatting issues, marketers typically assume compliance is being met in the background.
• HTML line breaks: A common point of confusion for marketers is how HTML line breaks (e.g., <br>) differ from RFC 5322's physical line length requirements.

Key considerations

• ESPs as gatekeepers: Marketers rely heavily on their ESPs to abstract away the technical complexities of email protocols. Issues with RFC 5322 compliance would generally indicate a bug or misconfiguration within the ESP's system.
• Monitoring bounce messages: While RFC 5322 issues are rare, marketers should still monitor bounce messages for any explicit mentions of RFC 5322 errors.
• Impact on deliverability: Even with strict formatting, deliverability success largely depends on sender reputation, list hygiene, and content quality, as highlighted by various sender guideline summaries.

Key opinions

• Developer concern: RFC 5322 formatting is a concern for developers of email software (MTAs/MUAs), not typically for end-users or marketers.
• ESP bug, not user error: If an email sent via an ESP violates RFC 5322, it's considered a bug that the ESP needs to address, not something the sender can typically fix on their own.
• No direct deliverability impact: RFC 5322 compliance issues are generally not the root cause of poor email deliverability for reputable senders.
• Alternative causes for poor deliverability: Problems with deliverability are more commonly attributed to poor address acquisition practices, sending irrelevant content, or issues with sender reputation.
• Header best practices: Basic adherence means avoiding duplicated essential headers (e.g., From, To, Subject) and ensuring correct line endings.

Key considerations

• Trust your ESP: If you are using a reputable ESP, you should generally trust that they are handling the technical nuances of RFC 5322 compliance.
• Beyond technical formatting: Focus efforts on improving list hygiene, segmenting audiences, personalizing content, and maintaining a positive sender reputation for better inbox placement, as these factors typically have a much greater impact on email deliverability.
• Diagnosing issues: If bounces explicitly mention RFC 5322 errors (e.g., abnormal characters), it warrants investigation and potentially engagement with your ESP's support.
• Measuring performance: It is essential to have reliable ways to measure and monitor your deliverability statistics, such as through Google Postmaster Tools, to understand how your emails are performing.

Key findings

• Format specification: RFC 5322 specifies the Internet Message Format (IMF), defining the syntax for email text messages.
• Required headers: It details essential header fields, including From, To, Subject, Date, and Message-ID.
• Line length rule: The standard specifies a maximum line length for the email body of 998 characters, including the newline characters.
• Character encoding: While US-ASCII is recommended, RFC 5322 permits the use of other character encodings (e.g., UTF-8) for email messages.

Key considerations

• Universal parsing: Adhering to RFC 5322 ensures that email clients and servers can correctly parse and display messages, preventing formatting issues and potential deliverability problems.
• Gmail's specific mandates: Gmail's guidelines specifically call for a valid Message-ID and proper formatting of headers like From, Subject, and Date, as these are crucial for message identification and spam filtering.
• Error indicators: Bounce messages citing RFC 5322 compliance errors (e.g., 554 5.3.4 message header size exceeds limit) indicate a structural problem that needs attention.
• Impact on deliverability: While not always the primary cause of spam classification, non-compliance with fundamental formatting can lead to messages being rejected or placed in the spam folder, particularly with strict receivers. This is part of the broader effort to ensure email compliance.