Is it possible to alias DKIM records, and what is NS delegation?
Michael Ko
Co-founder & CEO, Suped
Published 16 Jun 2025
Updated 17 Aug 2025
7 min read
When managing email infrastructure for clients, a common challenge arises: how to configure DNS records like DKIM without exposing the underlying email service provider (ESP) or requiring constant client involvement for DNS changes. I've encountered this firsthand, specifically when trying to alias DKIM records to create a layer of abstraction for our clients.
Initially, it might seem like a straightforward task to use CNAME records to point one DKIM entry to another, effectively aliasing it. However, the intricacies of how DNS resolvers handle these chains, especially with TXT records, can lead to unexpected behaviors. Furthermore, the concept of NS delegation provides a powerful alternative for agencies and large organizations managing multiple domains or subdomains for email sending.
This article explores whether aliasing DKIM records is truly possible and delves into the mechanics and benefits of NS delegation, offering insights into how these DNS strategies can impact email deliverability and management efficiency.
A common scenario involves an email service provider (ESP) like SendGrid providing a CNAME record for DKIM authentication. This record typically points from a subdomain on your client's domain (e.g., s1._domainkey.clientdomain.com) to a canonical hostname managed by the ESP (e.g., s1.domainkey.esp.net). The challenge arises when you want to insert another CNAME in this chain, making it s1._domainkey.clientdomain.com -> s1._domainkey.yourservice.com -> s1.domainkey.esp.net. My experience shows that while some ESPs might initially indicate this isn't possible, it can indeed work if the DNS records are precisely configured to maintain the correct full qualified domain names (FQDNs) in the CNAME chain.
The core issue often stems from how DNS resolvers handle CNAMEs and the specific requirements for DKIM. A DKIM record, defined in RFC 6376, is typically a TXT record containing the public key. When a CNAME points to another domain, the resolver is instructed to look for the final record at the target. This mechanism generally supports chaining, but inconsistencies can occur if the intermediate CNAME changes the expected subdomain structure or if the ESP's validation process is overly strict. One common pitfall is the inability to have a CNAME record at the same name as other records, which can cause issues if you're trying to add other DNS records alongside a CNAME at the same level.
The CNAME aliasing approach
Mechanism: Uses one or more CNAME records to redirect a DKIM lookup to another hostname. This can create a chain: client_domain -> your_service_domain -> esp_domain.
Control: The client retains control over their primary domain's DNS, with a specific CNAME entry pointing to your managed domain.
Flexibility: Limited, as changes to the underlying ESP's DKIM record might require updating the CNAME on the intermediate domain, which then impacts the client's configuration.
While it's technically possible to daisy-chain CNAMEs for DKIM, it's not always the most robust or recommended solution, especially when dealing with multiple clients or frequent changes in email service providers. The complexity of CNAME records and their interaction with TXT records can lead to validation issues or delays in propagation, which can impact email deliverability. The main benefit is abstracting the final destination, but it still requires some coordination for setup.
Understanding NS delegation
NS delegation, or Name Server delegation, is a more powerful and flexible approach for managing DNS records, particularly for specific subdomains. Instead of pointing individual records like CNAMEs or TXT records, NS delegation involves telling the parent domain's DNS that a specific subdomain's DNS records are now managed by a different set of name servers. This effectively hands over control of that subdomain's DNS zone to you or your designated DNS provider.
For example, if your client's main domain is clientdomain.com, they can set up NS records for email.clientdomain.com to point to your name servers (e.g., ns1.yourservice.com and ns2.yourservice.com). Once this is done, you have complete authority over all DNS records for email.clientdomain.com, including SPF, DKIM, DMARC, and MX records, without needing further access to the client's main DNS settings. You can learn more about DNS records generally, and how they operate, from resources such as Microsoft's Azure DNS documentation.
Example of NS delegationDNS
email.clientdomain.com. IN NS ns1.yourservice.com.
email.clientdomain.com. IN NS ns2.yourservice.com.
This method simplifies management significantly because all future changes related to the email subdomain, such as updating DKIM keys or switching ESPs, can be handled entirely on your side without bothering the client for DNS updates. This is crucial for maintaining efficient operations and ensuring consistent email deliverability.
Why NS delegation is often preferred
Comparing CNAME aliasing with NS delegation reveals clear advantages for the latter, especially in complex environments or when managing third-party email sending on behalf of other organizations.
CNAME aliasing
Setup: Requires a specific CNAME record on the client's main domain.
Management: Updates to the ESP's canonical DKIM records might necessitate changes at multiple points in the CNAME chain, requiring coordination.
Flexibility: Less flexible for switching ESPs or running multiple mail streams, as each might require its own CNAME entry.
NS delegation
Setup: Requires NS records for a subdomain on the client's main domain.
Management: Complete control over the delegated subdomain's DNS, allowing for all future changes without client intervention.
Flexibility: High flexibility for setting up DKIM on subdomains, DMARC, SPF, and managing multiple ESPs or sending infrastructure.
The main benefit of NS delegation lies in its ability to centralize DNS management for email-sending subdomains under your control. This means you can: easily spin up new email providers, warm up new infrastructure, and manage all related DNS records, including DKIM, SPF, and DMARC, without constant back-and-forth with your clients. This ensures quicker adjustments, fewer errors, and a more streamlined workflow for email operations.
Best practice for delegated subdomains
For email sending, always use a dedicated subdomain (e.g., mail.yourdomain.com) for NS delegation. This isolates your email reputation from your main domain's reputation and allows for more granular control over your sending infrastructure. It's a key part of improving overall email deliverability.
Although NS delegation is often the superior choice from a technical and operational standpoint, there can be challenges in getting clients to implement it. They might be unfamiliar with the process, hesitant to delegate control, or simply face internal hurdles. Clear communication about the benefits – simplified management, increased control, and better deliverability – can help overcome these initial resistance points.
Making the right choice for your email infrastructure
In summary, while directly aliasing DKIM records via a CNAME chain to mask your ESP can work under very specific and exact configurations, it often introduces unnecessary complexity and potential points of failure. The more robust and recommended solution, especially for agencies or organizations managing email for multiple brands, is NS delegation. This grants you full control over a dedicated email subdomain's DNS, enabling seamless management of all authentication records like DKIM, SPF, and DMARC.
This approach reduces client burden, simplifies transitions between email service providers, and empowers you to proactively manage your email sending infrastructure for optimal performance and deliverability. While implementing NS delegation requires an initial setup with the client's DNS provider, the long-term benefits in terms of flexibility and control far outweigh the effort.
For ongoing email health, regularly checking your domain's reputation and DNS configurations is essential. Being proactive about checking blocklists and monitoring your DMARC reports (using a DMARC monitoring tool) helps ensure your emails consistently reach the inbox.
Views from the trenches
Best practices
Always use a dedicated subdomain for email sending, especially for delegated DNS management, to separate reputation.
Prioritize NS delegation over complex CNAME chains for better long-term flexibility and control.
Clearly communicate the benefits of NS delegation to clients to streamline initial setup and minimize resistance.
Regularly review your delegated subdomain's DNS records to ensure all authentication mechanisms are correctly configured.
Common pitfalls
Attempting to alias DKIM records with intermediate CNAMEs can lead to unexpected DNS resolution issues.
Underestimating client reluctance to implement NS delegation due to unfamiliarity with DNS changes.
Not maintaining proper alignment between your SPF and DKIM records, which can impact email deliverability.
Failing to update DKIM keys periodically, which is important for security and compliance.
Expert tips
If your ESP offers CNAME records for DKIM, ensure the full hostname in your DNS matches exactly what they provide.
Consider NS delegation for large-scale operations or when managing email for multiple brands.
Use a DNS checker tool to verify that your DKIM records resolve correctly through any CNAME aliases or NS delegations.
Educate clients on the benefits of NS delegation for streamlined management and improved email deliverability.
Marketer view
Marketer from Email Geeks says that while their ESP initially said aliasing a DKIM record was not possible, they found that it worked when the CNAME records were set up with exact hostname matching.
2024-05-02 - Email Geeks
Expert view
Expert from Email Geeks says that many ESPs built on cloud platforms support this type of setup, where the backend checks for TXT and downstream records without necessarily validating the intermediate CNAME.
SendGrid providing a CNAME record for DKIM authentication. This record typically points from a subdomain on your client's domain (e.g., s1._domainkey.clientdomain.com) to a canonical hostname managed by the ESP (e.g., s1.domainkey.esp.net). The challenge arises when you want to insert another CNAME in this chain, making it s1._domainkey.clientdomain.com -> s1._domainkey.yourservice.com -> s1.domainkey.esp.net. My experience shows that while some ESPs might initially indicate this isn't possible, it can indeed work if the DNS records are precisely configured to maintain the correct full qualified domain names (FQDNs) in the CNAME chain.
