Summary
The consensus from experts, marketers, and documentation is that DKIM selectors are primarily a technical tool for key rotation and retrieval, and they do not directly influence email reputation. Email reputation is mainly associated with the DKIM signing domain (d=), the sending IP address, and overall email authentication practices (SPF, DKIM, DMARC). While some suggest mailbox providers *could* theoretically use selectors as a data point in machine learning, this is not standard, and using subdomains is a more effective approach to reputation segmentation.
Key findings
- Selector Function: DKIM selectors facilitate key rotation, enabling secure management of DKIM keys.
- Domain Reputation: Email reputation is primarily determined by the DKIM signing domain (d=).
- No Direct Influence: Selectors do not directly or significantly impact email reputation.
- Potential ML Use: Although not standard practice, mailbox providers could theoretically use selectors in machine learning models.
- Subdomain Alternative: Subdomains offer a more effective means of separating reputation than DKIM selectors.
- IP's Role: Sending IP address also plays a crucial role in email reputation.
Key considerations
- Key Management: Implement a robust key rotation strategy using selectors for security.
- Domain Focus: Prioritize building a positive reputation for the DKIM signing domain.
- Monitor ISP Practices: Stay informed about how different mailbox providers may be using DKIM data.
- Authentication Practices: Ensure SPF, DKIM, and DMARC are properly configured for comprehensive email authentication.
- Consider Subdomains: If you need to segment reputation, explore using subdomains for different email streams.
What email marketers say
13 marketer opinions
The general consensus is that DKIM selectors are primarily a technical mechanism for key rotation and do not directly influence email reputation. Email reputation is more closely tied to the DKIM signing domain (d=) and the sending IP address. While some sources suggest that mailbox providers could theoretically use selectors as a data point in machine learning algorithms for reputation assessment, it's not a common or recommended practice. Using subdomains is considered a better way to segment reputation.
Key opinions
- DKIM Selector Purpose: DKIM selectors are mainly used for key rotation, not reputation management.
- Domain Reputation: Email reputation is primarily associated with the DKIM signing domain (d=).
- Limited Direct Impact: Most sources indicate that DKIM selectors do not have a direct or significant impact on email reputation.
- Alternative Segmentation: Subdomains are a more effective method for separating email reputation compared to DKIM selectors.
- Machine Learning Possibility: While not recommended or common, selectors could theoretically be a data point in machine learning models for reputation assessment.
Key considerations
- Key Rotation: Properly implement DKIM key rotation using selectors to maintain security and prevent disruptions.
- Domain vs. Subdomain: Decide whether to use subdomains for separate email streams based on the desired level of reputation isolation.
- Holistic Approach: Focus on overall email authentication (SPF, DKIM, DMARC) and sending practices to build a positive sender reputation.
- ML Monitoring: Be aware of the possibility that mailbox providers might use selectors in their machine learning algorithms, though it's not a standard practice.
- Sending IP: The sending IP also plays a role in email reputation, especially for shared IP environments.
Marketer view
Marketer from Email Geeks shares that a common machine learning approach is to incorporate as many data points as possible, suggesting anything and everything could feed into reputation unless evidence indicates otherwise.
24 Oct 2023 - Email Geeks
Marketer view
Email marketer from MailerLite Blog implies that while DKIM itself improves deliverability and trust, they do not specifically mention DKIM selectors having a direct impact on email reputation but focus on the general DKIM setup.
28 Nov 2024 - MailerLite Blog
What the experts say
3 expert opinions
Experts generally agree that DKIM selectors are intended for key rotation and not for building email reputation. Reputation is primarily associated with the DKIM signing domain (d=) and sending IP. However, some Internet Service Providers (ISPs) might use selectors as a data point in machine learning models, even though this is not the intended use.
Key opinions
- Selector Purpose: DKIM selectors are designed for key rotation, not reputation management.
- Domain Importance: Email reputation is primarily linked to the DKIM signing domain (d=).
- Potential ISP Use: Some ISPs might use selectors as a data point in machine learning models, despite it not being the intended purpose.
Key considerations
- Key Rotation: Implement proper DKIM key rotation using selectors to maintain security.
- Domain Focus: Focus on building a positive reputation for the DKIM signing domain.
- ISP Monitoring: Be aware that some ISPs may use selectors in ways that deviate from the standard protocol.
Expert view
Expert from Email Geeks explains that you are absolutely not supposed to use selectors for reputation, but some ISPs do, noting that machine learning may identify selectors as a data point.
18 Nov 2023 - Email Geeks
Expert view
Expert from Spam Resource, John Levine, explains that while DKIM authenticates a message, the selector itself is primarily a technical mechanism for key rotation and doesn't directly influence email reputation. Reputation is generally tied to the domain (d=) and sending IP.
29 Jun 2022 - Spam Resource
What the documentation says
4 technical articles
Official documentation consistently states that DKIM selectors are primarily for key management and retrieval during the verification process. They are not designed to directly impact or segment email reputation. The DKIM signing domain (d=) and overall authentication health are more relevant factors for deliverability and reputation.
Key findings
- Key Retrieval: DKIM selectors are used to locate the public key needed for email verification.
- Key Management: Selectors facilitate key rotation, improving security.
- No Direct Reputation: Documentation does not indicate that selectors directly influence email reputation.
- Domain Importance: The DKIM signing domain (d=) is a key factor in assessing email reputation.
- Holistic Authentication: Overall authentication health (SPF, DKIM, DMARC) is crucial for deliverability.
Key considerations
- Proper Configuration: Ensure DKIM selectors are correctly configured to enable key retrieval.
- Key Rotation Strategy: Implement a robust DKIM key rotation strategy using selectors.
- Domain Reputation: Focus on building a positive reputation for the DKIM signing domain.
- Authentication Practices: Implement SPF, DKIM, and DMARC for comprehensive email authentication.
Technical article
Documentation from Microsoft explains email authentication using SPF, DKIM, and DMARC to improve deliverability and protect from spoofing, but does not provide specific information on DKIM selectors affecting email reputation. Focuses on authenticating the sending domain.
1 Mar 2025 - Microsoft
Technical article
Documentation from Google states strong authentication practices (SPF, DKIM, and DMARC) improve deliverability but does not single out DKIM selectors as individual reputation factors. Focus is on overall domain authentication health.
2 Nov 2023 - Google
Are people using 4096-bit DKIM keys, and what is the recommended DKIM key length?
Can DKIM be set up on a subdomain, and which domain should be used for signing?
Do I need multiple DKIM records if I use multiple ESPs like HubSpot, Sendgrid and ActiveCampaign?
How do I find the DKIM selector for my domain in Dmarcian or Hubspot?
How does changing DKIM selectors impact email reputation and what are the best practices for key rotation?
How should DKIM selector names be interpreted and what is the recommended DKIM key size?
Why does DKIM authentication sometimes fail with certain ISPs or receivers like Barracuda and Proofpoint?
Why is DKIM failing and how do I set it up for a subdomain?
