Summary
Experts and documentation provide a comprehensive overview of SPF records and email deliverability for small mail servers. Key takeaways include the danger of useless SPF records and a skeptical perspective on SPF itself. Experience shows Gmail might not always treat emails from small servers as bulk. Unknown IPs are often considered spam. A critical limit of 10 DNS lookups exists, and common errors include exceeding this limit, incorrect syntax, and omitting sending sources. SPF flattening and simple records can mitigate lookup issues. For Exchange Online, including Microsoft's servers is essential. The SPF specification (RFC 4408) outlines the framework. Permissive SPF records (?all or ~all) are risky. Regular monitoring, validation, and third-party sender inclusion are best practices. A hard fail (-all) is recommended. Multiple SPF records are detrimental. DNS propagation time matters. DMARC alignment is crucial, and mail forwarding can introduce complexities addressed by rewriting the envelope sender. Finally, the 'exists' mechanism in SPF should be avoided due to its inefficiency.
Key findings
- SPF Dangers: Useless or poorly configured SPF records can harm deliverability.
- Gmail Behavior: Gmail may not automatically classify emails from small servers as bulk.
- IP Reputation: Emails from unknown IPs are often treated as spam.
- DNS Lookup Limit: SPF records are limited to 10 DNS lookups.
- Common Errors: Exceeding lookups, incorrect syntax, and omitting sources are frequent mistakes.
- Permissive Records Risks: Permissive SPF records (?all or ~all) can be exploited.
- Forwarding Issues: Mail forwarding can disrupt SPF authentication.
- 'Exists' Inefficiency: The 'exists' mechanism in SPF is slow and generally unhelpful.
- DMARC alignment: Requires alignment in order to pass.
Key considerations
- Record Quality: Ensure your SPF record is valid and functional.
- Limit Management: Carefully manage the number of DNS lookups in your SPF record; consider flattening.
- Service Requirements: Adhere to specific requirements for services like Exchange Online.
- Security: Avoid permissive records and use a hard fail (-all) for better security.
- Regular Maintenance: Monitor, validate, and update your SPF record regularly.
- Comprehensive Coverage: Include all sending sources, especially third-party services.
- Propagation Awareness: Account for DNS propagation time after making changes.
- Forwarding Strategy: Implement strategies to handle mail forwarding appropriately.
- IP warmup: Warm up new sending IPs to build a sending reputation.
What email marketers say
10 marketer opinions
Several common misconceptions and best practices regarding SPF records and email deliverability for small mail servers were identified. Common errors include exceeding DNS lookup limits, incorrect syntax, and not including all sending sources. It's a misconception that permissive SPF records (?all or ~all) are always safe, as they can be exploited by spammers. Best practices include using SPF flattening to reduce DNS lookups, regularly monitoring SPF records, simplifying SPF records, validating syntax, including all third-party senders, using a hard fail (-all), avoiding multiple SPF records, and accounting for DNS propagation time. Proper SPF record implementation is essential for ensuring email authentication and improving deliverability, especially for small mail servers.
Key opinions
- Common SPF Errors: Common errors include too many DNS lookups, incorrect syntax, and failing to include all sending sources.
- Permissive Records: Permissive SPF records (?all or ~all) are not always safe and can be exploited.
- Importance of Monitoring: Regular monitoring of SPF records and authentication results is crucial.
- Record Simplification: Keeping SPF records simple helps avoid exceeding lookup limits.
- Third-party inclusion: All third-party senders should be included in your SPF record to be authenticated.
- Hard Fail: Using a hard fail (-all) improves deliverability and security.
- No Multiple Records: Avoid having multiple SPF records; combine all mechanisms into one.
Key considerations
- DNS Lookup Limit: Ensure your SPF record does not exceed the 10 DNS lookup limit; use SPF flattening if necessary.
- Record Validation: Regularly validate your SPF record syntax to prevent errors.
- DNS Propagation: Account for DNS propagation time when making changes to your SPF record.
- Complete Sender List: Ensure all sending sources, including third-party senders, are included in your SPF record.
- Security: Balance deliverability and security and use a hard fail and review the implications for forwards and third parties.
Marketer view
Email marketer from MXToolbox shares the best practice of using tools like MXToolbox to validate your SPF record syntax and ensure it doesn't contain errors that could impact deliverability.
26 Jun 2024 - MXToolbox
Marketer view
Email marketer from EmailOnAcid advises including all third-party senders (e.g., marketing automation platforms, transactional email services) in your SPF record to ensure their emails are authenticated.
2 Sep 2021 - EmailOnAcid
What the experts say
7 expert opinions
Experts highlight several key points regarding SPF records and email deliverability for small mail servers. One expert emphasizes the danger of useless SPF records, while another views SPF with skepticism. Experiences with a small mail server show that Gmail doesn't automatically treat mail as bulk even without specific SPF configurations. Sending from previously unknown IPs often results in emails being marked as spam. Common SPF mistakes include exceeding DNS lookup limits, not including all sending sources, and incorrect syntax. Forwarding mail can cause issues with SPF records, potentially requiring rewriting the envelope sender. The 'exists' mechanism in SPF is often slow and not particularly helpful. These insights stress the importance of careful SPF record configuration and awareness of potential pitfalls.
Key opinions
- Useless SPF Records: Some SPF records can be downright harmful to your email deliverability, so only use correct records.
- Gmail Handling: Gmail doesn't always treat emails from small servers as bulk, even without specific SPF configurations.
- Unknown IPs: Emails from previously unknown IPs are often flagged as spam.
- Common SPF Errors: Exceeding DNS lookup limits, not including all sending sources, and incorrect syntax are common SPF mistakes.
- Forwarding Issues: Mail forwarding can create SPF problems, potentially requiring rewriting the envelope sender.
- Exists Mechanism: The 'exists' mechanism in SPF is often slow and not very helpful.
Key considerations
- SPF Record Quality: Ensure your SPF record is not useless and doesn't negatively impact deliverability.
- IP Reputation: Be aware that sending from previously unknown IPs may initially result in emails being flagged as spam, and plan to address this.
- Record Limits: Manage your SPF record to stay within the 10 DNS lookup limit.
- Forwarding Strategy: Understand how forwarding affects SPF and implement solutions like rewriting the envelope sender if necessary.
- Mechanism choice: Avoid using the 'exists' mechanism because its slow and not helpful.
Expert view
Expert from Email Geeks shares her experience with a small mail server, noting that Gmail didn't put their mail into bulk, even after moving the server and not publishing -all. She uses this as a counterexample to claims of Gmail being evil.
16 Jan 2025 - Email Geeks
Expert view
Expert from Email Geeks shares his perspective on SPF, stating, "I don't believe in SPF in the way I don't believe in parking tickets, not in the way I don't believe in bigfoot."
25 Sep 2022 - Email Geeks
What the documentation says
4 technical articles
Documentation from various sources highlights crucial aspects of SPF records and their impact on email deliverability. Google's documentation emphasizes the 10 DNS lookup limit, while Microsoft advises including their servers' SPF record for Exchange Online. RFC 4408 specifies the SPF framework and its limitations. DMARC.org clarifies that for DMARC to pass via SPF, the domain in the `Mail From` address must align with the domain in the SPF record. These points underscore the importance of adhering to SPF specifications, managing DNS lookups, and ensuring proper alignment for DMARC compliance.
Key findings
- DNS Lookup Limit: SPF records have a 10 DNS lookup limit, which can cause deliverability issues if exceeded.
- Exchange Online Requirement: For Exchange Online, including Microsoft's servers in your SPF record is necessary.
- SPF Specification: RFC 4408 defines the SPF framework and its limitations, crucial for understanding SPF's functionality.
- DMARC Alignment: For DMARC to pass with SPF, the domain in the `Mail From` address must align with the domain used in the SPF record.
Key considerations
- Lookup Management: Carefully manage the number of DNS lookups in your SPF record to stay within the limit.
- Service Requirements: Follow specific guidelines for services like Exchange Online to ensure proper SPF configuration.
- Specification Adherence: Adhere to the SPF specification outlined in RFC 4408 to avoid syntax and functional issues.
- DMARC Compatibility: Ensure your SPF record is configured in a way that supports DMARC alignment for enhanced email security and deliverability.
Technical article
Documentation from DMARC.org clarifies that for DMARC to pass based on SPF, the domain in the `Mail From` address (Return-Path) must align with the domain used in the SPF record. This is a common misconception that affects DMARC compliance.
12 Jan 2025 - DMARC.org
Technical article
Documentation from Google Workspace Admin Help explains that SPF records have a lookup limit of 10, which can cause issues if exceeded, impacting deliverability. Exceeding the limit can cause SPF checks to fail.
13 Jan 2022 - Google Workspace Admin Help
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