This error message is shown when Microsoft 365 cannot locate a required CNAME record in your domain’s public DNS. The error typically arises during various steps, such as domain setup, when activating DomainKeys Identified Mail (DKIM), or when enabling services like Autodiscover, a Microsoft feature that configures mail clients automatically. Microsoft 365 checks your domain’s authoritative nameservers, and if the necessary CNAME record is missing, misconfigured, or obscured by a proxy, you will encounter this warning.
A CNAME (Canonical Name) record acts as an alias, pointing one hostname to another. Many essential Microsoft 365 features, such as DKIM, Autodiscover, Intune, and Teams, depend on these CNAME records. Resolving this issue is straightforward once you confirm the precise host and target values expected by Microsoft 365.
Begin by navigating to the Microsoft 365 admin center. Go to Settings, then Domains, and select your domain. Under DNS records, you will find the required hostnames and target values. For DKIM, access Security > DKIM and copy both selector records using the provided copy buttons to avoid typos.
For readers unfamiliar with these terms, consider reviewing a primer on SPF, DKIM, and DMARC. This guide will clarify why these CNAME records are critical for email authentication.
Confirm the DNS record is live from outside your local network using command-line tools. Replace example.com with your actual domain.
nslookup -type=cname selector1._domainkey.example.comnslookup -type=cname autodiscover.example.comOn macOS or Linux, use dig:
dig +short CNAME selector1._domainkey.example.comdig +trace selector1._domainkey.example.comExpected result: These commands should return the target hostname exactly as entered, without SERVFAIL or NXDOMAIN errors. An NXDOMAIN result means the record does not exist in public DNS. If you see a different target, another record may be shadowing your intended CNAME.
If you find the process challenging, you can query your domain’s authoritative nameservers directly. Compare the result with what you receive from a public resolver like 1.1.1.1. Differences may indicate issues with caching or outdated delegation.
dig or nslookup returns the expected target value.A missing CNAME often suggests that DKIM may have been inactive for a period, such as several days or weeks. During this time, your emails could have been diverted to spam or junk folders, resulting in negative signals within recipient filters such as Outlook. These filters log and remember poor sender reputations.
To improve your email deliverability after resolving DNS issues, consider a process called warming up. This involves gradually increasing your email sending volume, allowing filters to relearn your good reputation and improving inbox placement.
Tools like Mailwarm offer automated, gradual engagement across a network of monitored inboxes. These services open, reply, and move messages out of spam folders, marking them as important or primary, which helps rebuild sender reputation authentically and securely. Unlike marketing tools, these warming solutions focus on technical legitimacy, not mass outreach.
The recommended approach is as follows: fix your DNS records, confirm that DKIM is active, start with a controlled warm-up, and keep your email volume stable. If you’d like an expert perspective, reach out to the deliverability team at mailadept their insights can save you days of unnecessary troubleshooting.
This error indicates that Microsoft 365 cannot find a necessary CNAME record during domain setup or service activation like DKIM or Autodiscover. Misconfigured DNS settings or proxying often obscure these critical records, causing failures.
Access your Microsoft 365 admin center to verify the expected host and target values. Missteps like using auto-appended domains or conflicting records often lead to issues. Check your DNS provider's requirements for entry format meticulously.
Common errors include inadvertently duplicating the domain in hostnames due to auto-appending settings and mixing CNAME with TXT records. Critical functions like DKIM will fail without precise adherence to record configuration specifications.
When providers like Cloudflare proxy DNS CNAME records, validation checks can fail due to obscured DNS data. Provision CNAME records as DNS-only to ensure accessibility and prevent disruption of services like DKIM and Autodiscover.
Days or weeks without proper CNAME records may label your emails as spam due to inactive DKIM. This leads to detrimental sender reputations, requiring a deliberate warm-up period to re-establish trust and enhance deliverability.
Traditional DNS does not support CNAME records at the domain apex, which can break essential services. Microsoft 365 doesn't need CNAMEs at the root for email functionality, thus avoiding potential conflicts and misconfigurations.
Ensure no conflicting records co-exist and that CNAME settings are DNS-only without CDN interference. Public DNS checks through dig or nslookup must verify the correct target value to proceed with validation.
If DNS updates seem ineffective, old or incorrect nameservers may be the culprits. Confirm your registrar points to the right nameservers and allows sufficient propagation time to reflect changes globally.


