PTR Record Error When Sending Email via Microsoft 365 – Domain on Route 53 with CDN

The PTR record error you're experiencing when sending emails via Microsoft 365 with your Route 53 domain is likely related to DNS configuration issues. Here are some potential causes and solutions:

1. PTR Record Mismatch: PTR records (reverse DNS) map IP addresses back to domain names and are crucial for email delivery. When Microsoft 365 sends emails from their servers, the receiving mail servers check if the sending IP has a valid PTR record. This is not something you configure in Route 53, but rather something Microsoft manages for their sending infrastructure.

2. DNS Configuration Issues: Even though your issue mentions PTR records specifically, the problem might be related to other DNS misconfigurations:

• Nameserver Mismatch: Ensure that the nameservers listed in your domain registration match exactly with those in your Route 53 hosted zone. Mismatched nameservers can cause DNS resolution failures.

• Incomplete DNS Propagation: After adding or modifying DNS records, it can take 24-48 hours for changes to fully propagate across the internet.

3. Email Authentication Records: Verify that all required email authentication records are properly configured:

• SPF Records: Ensure your SPF record includes Microsoft 365's sending servers.
• DKIM Records: Check that DKIM is properly configured for your domain in Microsoft 365.
• DMARC Record: Consider adding a DMARC record if you haven't already.

4. CDN Interference: While your CDN (CloudFront) should only affect web traffic and not email delivery, ensure there are no conflicting DNS settings between your CDN configuration and email-related DNS records.

5. Verification Steps:

• Use DNS lookup tools to verify your DNS records are visible publicly
• Check that all required records for Microsoft 365 are present and formatted correctly
• Verify your domain in Microsoft 365 to ensure it recognizes your DNS configuration

If you've verified all these points and are still experiencing issues, you may need to contact Microsoft 365 support, as the PTR record issue might be on their end rather than with your Route 53 configuration.
Sources
Email DNS Issues after Transfer to AWS Route 53 | AWS re:Post
DNS Error: SERVFAIL | AWS re:Post
SOA Record from Route57 register domain cannot be found by DNSchecker.org | AWS re:Post