Email DNS Record Checker

SPF (Sender Policy Framework) specifies which mail servers are authorized to send email on behalf of your domain. It's a whitelist published in DNS that receiving servers check against the sending server's IP address. DKIM (DomainKeys Identified Mail) uses cryptographic signatures to verify that email content hasn't been tampered with during transit—your mail server adds a digital signature using a private key, and receiving servers verify it using the public key published in your DNS.

DMARC (Domain-based Message Authentication, Reporting, and Conformance) builds on SPF and DKIM by adding policy enforcement and reporting. It tells receiving servers what to do when SPF or DKIM checks fail (none, quarantine, or reject) and provides aggregate reports showing who's sending email using your domain. Think of SPF as verifying the sender's identity, DKIM as ensuring message integrity, and DMARC as the policy framework that ties them together and provides visibility. For maximum protection and deliverability, you should implement all three—they work synergistically, with each covering gaps the others leave.

DNS propagation typically takes 1-48 hours, though most changes are visible within 4-6 hours. The exact timing depends on your domain's TTL (Time To Live) settings—shorter TTLs mean faster propagation but more DNS queries. If your current records have a TTL of 86400 (24 hours), it could take a full day for all DNS servers globally to update their caches.

To expedite future changes, consider lowering your TTL to 300-600 seconds (5-10 minutes) a few days before making critical updates, then raising it back after changes are confirmed. You can check propagation status using DNS checking tools that query multiple servers worldwide. Note that even after propagation completes, email servers may cache authentication results for several hours, so allow 24-48 hours of real-world sending before judging the impact of DNS changes. During this period, monitor bounce messages and use email header analyzers to verify that authentication is passing.

Yes, multiple DKIM records are not only possible but recommended when using multiple email services. Each service uses a unique selector (like "google._domainkey" for Google Workspace or "k1._domainkey" for Mailchimp), allowing them to coexist without conflict. When an email is sent, the service includes its selector in the DKIM-Signature header, telling receiving servers which public key to use for verification.

For example, you might have google._domainkey.yourdomain.com for Google Workspace, default._domainkey.yourdomain.com for your web application, and k1._domainkey.yourdomain.com for your marketing platform. Each service manages its own private/public key pair independently. This is actually more secure than sharing a single DKIM key across services, as it provides isolation—if one service's key is compromised, the others remain secure. When setting up multiple DKIM records, ensure each service uses a distinct selector, keep track of which selector belongs to which service, and rotate keys regularly (annually is a best practice).

SPF authentication is just one of many factors email providers use to determine inbox placement. A valid SPF record means you've passed authentication, but spam filtering also considers sender reputation, content quality, engagement metrics, DKIM/DMARC status, domain age, and complaint rates. If your SPF passes but emails still reach spam, investigate these other factors.

Common culprits include: missing or weak DMARC implementation (many providers now require this), low sender reputation from previous delivery issues, spam-like content triggers (excessive caps, misleading subjects, too many links), lack of proper list hygiene (high bounce rates, spam traps), sudden volume spikes that trigger filters, or recipients marking your emails as spam. Check your sender score using tools like SenderScore or Google Postmaster Tools. Ensure DKIM and DMARC are also properly configured—providers like Gmail and Yahoo now require all three for bulk senders. Implement a warm-up schedule if you're a new sender, gradually increasing volume over 2-4 weeks. Most importantly, focus on engagement: providers promote emails that recipients open, click, and interact with, while demoting emails that are ignored or deleted unread.

It depends on whether you're sending email from subdomains and your DMARC configuration. SPF and DKIM records don't inherit from the parent domain—if you send email from newsletter.example.com, it needs its own SPF record, even if example.com has one. However, DMARC has an inheritance mechanism: if no DMARC record exists for a subdomain, receiving servers check the organizational domain's DMARC policy.

Best practice is to create explicit DMARC records for subdomains you actively use for email, with policies appropriate to that subdomain's purpose. For subdomains you don't use for email, the parent domain's DMARC policy provides protection. If you want to explicitly prevent a subdomain from being used for email (which blocks spoofing attempts), create a restrictive SPF record like "v=spf1 -all" and a reject DMARC policy like "v=DMARC1; p=reject;" for that subdomain. This approach is particularly important for common subdomains like www, ftp, or dev that attackers might try to abuse. Monitor your DMARC reports to identify any legitimate email sources you might have overlooked on subdomains.

Perform comprehensive DNS checks quarterly at minimum, with additional checks whenever you make infrastructure changes. Email authentication can break silently—your mail server continues sending, but deliverability gradually degrades as authentication failures accumulate. Regular monitoring catches issues before they impact business operations. Schedule checks after any email provider migration, DNS hosting changes, addition or removal of email services, or updates to marketing automation platforms.

For enterprise environments or high-volume senders, implement continuous monitoring with automated alerts. Many DNS monitoring services can check your records daily and notify you of changes or failures. Pay special attention to SPF records, which can break when you add includes without checking the lookup limit, and DKIM records, which fail when keys expire or are rotated without updating DNS. Also review DMARC aggregate reports weekly—they reveal authentication failures you might not otherwise notice. Consider setting up a dedicated email address for DMARC reports (rua=mailto:dmarc-reports@yourdomain.com) and use a DMARC analysis tool to parse the XML reports into actionable insights. This proactive approach prevents the common scenario where businesses discover authentication problems only after major delivery issues have already damaged sender reputation.