Email delivery failures are one of the most common and frustrating challenges for businesses and individuals alike. While there are many reasons for email delivery issues such as incorrect email addresses, server problems, or user settings one of the most significant causes is issues with DNS (Domain Name System) configuration. DNS-related email delivery failures can prevent legitimate emails from reaching their intended recipients, leading to lost communications, delayed responses, and potential reputational damage.

This knowledgebase explores how DNS issues can affect email delivery, the common causes of DNS-related email delivery failures, and how to troubleshoot and resolve these problems to ensure successful email communication.

How DNS Affects Email Delivery

Before diving into solutions, it’s important to understand how DNS affects email delivery. DNS is the system that translates human-readable domain names into machine-readable IP addresses, allowing email servers to locate each other over the internet. It plays a vital role in various email functions, including domain verification, sender authentication, and the delivery process itself.

Here are the key DNS components related to email delivery:

• MX Records (Mail Exchange Records): MX records are DNS records that indicate the mail servers responsible for receiving emails on behalf of a domain. These records point to the IP address or domain name of the email server and determine where incoming email for a specific domain should be routed.

• SPF Records (Sender Policy Framework): SPF is a DNS record that specifies which IP addresses are authorized to send emails on behalf of a domain. This helps to prevent email spoofing and ensures that emails are sent from trusted sources.

• DKIM Records (DomainKeys Identified Mail): DKIM is a protocol that uses DNS to store public cryptographic keys. It allows email receivers to verify that the sender is authorized to send emails on behalf of the domain and ensures the email’s integrity during transit.

• DMARC Records (Domain-based Message Authentication, Reporting, and Conformance): DMARC is an email authentication protocol that leverages SPF and DKIM to help prevent phishing and spoofing attacks. It uses DNS to publish policies that tell receiving mail servers how to handle email that fails authentication.

• PTR Records (Pointer Records): These records are used for reverse DNS lookups. When a mail server sends an email, the recipient’s server will often perform a reverse DNS lookup to ensure the IP address of the sending server matches its domain name. A missing or incorrect PTR record can cause emails to be flagged as suspicious.

Common DNS-Related Causes of Email Delivery Failures

While DNS plays a crucial role in email delivery, misconfigured or absent DNS records can cause significant email delivery failures. The most common DNS-related causes of email issues include:

Incorrect MX Records

MX records are essential for directing emails to the right mail server. If your MX records are incorrectly configured, incoming emails will not be routed to the correct mail server, resulting in failed delivery.

Common Issues:

• Missing or incorrect MX records.
• Pointing MX records to an inactive or wrong mail server.
• Misconfigured priority values (MX records have priority values to determine the order in which mail servers are tried).

Missing or Incorrect SPF Records

SPF (Sender Policy Framework) records are used to authenticate the sender’s server and prevent spoofing. If your SPF record is incorrect or missing, receiving servers may reject your emails or mark them as spam.

Common Issues:

• Missing or incorrectly configured SPF record.
• SPF record doesn’t include all IP addresses used to send emails.
• SPF record exceeds the DNS lookup limit (10 lookups).

Missing or Incorrect DKIM Records

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to emails, ensuring the sender is authorized to send emails on behalf of the domain. If DKIM records are missing or incorrect, receiving mail servers might reject your email or mark it as suspicious.

Common Issues:

• Missing DKIM records in DNS.
• Incorrect DKIM selector used.
• DKIM's public key doesn’t match the private key used to sign outgoing emails.

Missing PTR Records for Reverse DNS Lookup

PTR records are necessary for reverse DNS lookups, ensuring that the sender’s IP address matches the domain it claims to represent. If PTR records are missing or incorrect, emails from the sending domain may be flagged as spam or rejected outright.

Common Issues:

• Missing PTR record for your sending mail server’s IP.
• PTR record does not match the domain name used by the mail server.

Misconfigured DMARC Records

DMARC (Domain-based Message Authentication, Reporting, and Conformance) records are used in conjunction with SPF and DKIM to authenticate emails and help prevent phishing. If DMARC records are misconfigured, emails might not pass the authentication checks, leading to delivery failures or emails being marked as spam.

Common Issues:

• Missing DMARC records.
• Incorrect DMARC policies (e.g., p=none instead of p=reject).
• Invalid DMARC syntax or misconfigured alignment with SPF and DKIM.

DNS Propagation Delays

When you update DNS records, such as adding or modifying MX, SPF, DKIM, or DMARC records, changes can take time to propagate throughout the internet. During this time, email servers might still rely on the old records, causing delivery failures.

Common Issues:

• DNS changes not propagating across all servers.
• Cached DNS records not reflecting updates.

How to Fix DNS-Related Email Delivery Failures

If you are experiencing DNS-related email delivery failures, you can take the following steps to troubleshoot and resolve the issues:

Verify MX Records

1. Check your MX records: Use a DNS lookup tool to check that your MX records are correctly pointing to the correct mail server.
2. Ensure correct priority values: MX records include a priority value. Lower numbers have higher priority. Ensure that your records are configured correctly and that they are pointing to active mail servers.
3. Update MX records if necessary: If your mail server changes, you may need to update your MX records to point to the new server.

Set Up or Correct SPF Records

1. Check your SPF record: Use an SPF checker tool like Kitterman’s SPF Validator to ensure your SPF record exists and is properly formatted.
2. Include all mail servers: Make sure that your SPF record includes all IP addresses and third-party services (like email marketing platforms or CRM systems) that send emails on your behalf.
3. Limit DNS lookups: SPF records can have a maximum of 10 DNS lookups. If you exceed this limit, you’ll need to optimize your SPF record by removing unnecessary mechanisms or including them in other records.

Implement or Fix DKIM Records

1. Check DKIM records: Use a tool like DKIMCore to check your DKIM records.
2. Ensure correct selector and key: Ensure that the DKIM selector in your DNS record matches the selector used by your email server and that the public key is correct.
3. Sign emails: Ensure your email server is configured to sign outgoing emails with the correct private key.

Add or Correct PTR Records

1. Check PTR records: Use a reverse DNS lookup tool like MXToolbox Reverse DNS to check if your mail server’s IP address has a valid PTR record.
2. Ensure PTR matches domain: The PTR record should match the domain name of your mail server. If it doesn’t, contact your hosting provider or DNS administrator to correct it.
3. Verify with your ISP or hosting provider: Some ISPs or cloud hosting providers handle PTR records, so reach out to them if you need assistance.

Set Up or Correct DMARC Records

1. Check your DMARC record: Use a tool like DMARC Analyzer to check if your DMARC record exists and is properly formatted.
2. Set a strict DMARC policy: For better email protection, set your DMARC policy to p=reject prevent unauthenticated emails from being delivered.
3. Ensure SPF and DKIM alignment: DMARC requires that SPF and DKIM align with the domain in the From address. Ensure that your records are configured for alignment.

Wait for DNS Propagation

• Be patient: DNS updates can take up to 48 hours to fully propagate across all servers. During this time, email delivery might still be affected.
• Use DNS propagation tools: You can use tools like checking if your DNS changes have propagated worldwide.

Best Practices to Prevent DNS-Related Email Delivery Failures

1. Implement SPF, DKIM, and DMARC: These records are essential for authenticating your domain and ensuring that your emails are delivered successfully and securely.
2. Monitor DNS records regularly: Regularly check your DNS records to ensure they’re correctly configured. Set up monitoring tools to alert you if there are any changes or issues.
3. Use professional email services: If you’re using third-party email providers or sending emails on behalf of your domain, ensure that their IP addresses are included in your SPF record and that they’re properly authenticated.
4. Backup your DNS records: Make regular backups of your DNS records so you can quickly restore them in case of accidental deletion or corruption.
5. Consult with your DNS and hosting provider: If you’re unsure about your DNS records or email configuration, consult with your DNS or hosting provider to get expert advice.

Usage Field: Get Rid of DNS-Related Email Delivery Failures

DNS-related email delivery failures occur when email servers are unable to authenticate or route emails correctly due to misconfigurations in DNS settings. Resolving DNS issues is critical for ensuring successful email communication, maintaining a good sender reputation, and improving deliverability rates. Here’s an overview of where and how fixing DNS-related email delivery failures is essential:

1. Corporate Email Systems: Ensuring that emails sent from a corporate domain are not marked as spam or rejected by recipients is vital for maintaining business communication. Proper DNS configuration ensures smooth and secure email delivery to clients and employees.

2. E-commerce Platforms: For online stores, email is a primary method for customer communication, order confirmations, and marketing campaigns. DNS-related failures can cause missed transactions and customer dissatisfaction. Proper DNS settings prevent lost orders and customer confusion.

3. Marketing Campaigns: Many marketing campaigns rely heavily on email. Misconfigured DNS settings, like SPF and DKIM records, can result in emails being flagged as spam or failing to deliver. Correct DNS configuration helps ensure higher email open rates and engagement.

4. Email Service Providers (ESPs): ESPs such as Mailchimp, SendGrid, or Amazon SES rely on correct DNS settings for seamless email delivery. DNS issues can cause email deliverability failures, impacting the effectiveness of mass email campaigns.

5. Transactional Emails: Automated emails like password resets, account activations, and invoices must be delivered promptly. DNS failures can delay or block these essential messages. Configuring DNS records such as MX, SPF, DKIM, and DMARC ensures critical email flow.

6. Domain Reputation: DNS misconfigurations can negatively impact your domain’s reputation with ISPs and email providers. If emails repeatedly fail to deliver due to DNS errors, email servers may start treating your emails as spam. Proper DNS configuration helps maintain a positive sender reputation.

7. Customer Support: Resolving DNS issues is essential for customer support systems that use email for case updates and resolution tracking. Ensuring that your DNS records are configured correctly ensures smooth communication with customers.

8. Compliance and Security: Email security protocols like SPF, DKIM, and DMARC help prevent phishing and spoofing attacks. Correct DNS configuration ensures compliance with security standards and protects your organization from impersonation.

9. Brand Consistency: Consistent and reliable email communication is key to maintaining brand credibility. DNS issues can disrupt email continuity, leading to confusion and brand damage. The proper configuration ensures brand consistency in email interactions.

10. Improved Deliverability: Proper DNS settings increase the chances of your email landing in the recipient’s inbox, rather than being marked as spam. This increases email open rates and reduces the likelihood of email delivery failure.

Technical Issue: DNS-Related Email Delivery Failures

DNS-related email delivery failures are caused by several potential issues in the configuration of DNS records. The most common technical issues that can result in email delivery failures include the following:

Missing or Misconfigured MX Records

• Technical Issue: MX records are essential for routing emails to the correct mail server. If the MX records are missing or incorrectly configured, emails will not be delivered to the correct destination.
• Solution: Ensure that your MX records point to the correct mail servers and that the priority values are correctly configured.

Incorrect or Missing SPF Records

• Technical Issue: SPF records specify which IP addresses or servers are authorized to send emails on behalf of your domain. A missing or incorrectly configured SPF record may cause receiving servers to reject or flag your emails as spam.
• Solution: Add or correct your SPF record to include all authorized sending IPs. Ensure it does not exceed the limit of 10 DNS lookups.

Invalid DKIM Records

• Technical Issue: DKIM records are used for email signature verification, confirming that the email was sent by an authorized sender. Invalid DKIM records can cause emails to fail verification, leading to rejection or marking as spam.
• Solution: Verify that your DKIM records are set up correctly, and ensure the public key in DNS matches the private key used by your mail server.

Missing or Incorrect DMARC Records

• Technical Issue: DMARC records define how an email should be handled if it fails SPF or DKIM checks. A missing or improperly configured DMARC record can result in undelivered or misclassified emails.
• Solution: Add or correct your DMARC record to ensure alignment with SPF and DKIM policies. Use the p=reject policy for better security.

Missing Reverse DNS (PTR) Records

• Technical Issue: Reverse DNS records (PTR) are required for reverse lookups, confirming that the sending IP matches the domain name. Without a valid PTR record, emails might be flagged as suspicious and rejected.
• Solution: Set up reverse DNS records for your sending IP addresses, ensuring they match the domain name used by your mail server.

Incorrect or Expired DNS Records

• Technical Issue: DNS records that are outdated or expired can cause email delivery failures. This is particularly common when DNS records are updated but the changes haven't propagated or if TTL (Time to Live) settings are misconfigured.
• Solution: Review your DNS records regularly and verify that the TTL values are appropriate. Allow time for DNS changes to propagate.

DNS Propagation Delays

• Technical Issue: When DNS records are updated, changes may not propagate immediately, causing delivery failures in the interim. This delay can range from a few minutes to 48 hours.
• Solution: Be patient and monitor DNS propagation using tools Verify if your changes have been applied globally.

DNS Lookup Limits Exceeded (SPF Records)

• Technical Issue: SPF records are limited to 10 DNS lookups. If an SPF record exceeds this limit, email servers will fail to process the SPF check and may reject the email.
• Solution: Optimize your SPF record by removing unnecessary include statements or by consolidating records.

Configuration Errors in DNS Server Settings

• Technical Issue: Errors in DNS server settings can cause incorrect routing or failed DNS queries. This can lead to email delivery failures if DNS records are not properly resolved.
• Solution: Ensure that DNS servers are configured correctly, and run diagnostic tools to check for errors or inconsistencies.

DNS Caching Issues

• Technical Issue: DNS caching can cause outdated or incorrect DNS records to be used, even if the records have been updated. This can result in intermittent email delivery failures.
• Solution: Clear the DNS cache on both sending and receiving servers or lower the TTL values for more frequent updates.

Technical FAQ: Get Rid of DNS-Related Email Delivery Failures

What is an MX record, and why is it important for email delivery?

• Answer: MX (Mail Exchange) records define which mail server is responsible for receiving emails for a particular domain. If the MX records are misconfigured or missing, emails will not reach the correct server, resulting in delivery failures.

How can I check if my MX records are set up correctly?

• Answer: Use an online tool to perform a DNS lookup and verify that your MX records point to the correct mail servers. Ensure that the priority and server addresses are accurate.

What should I do if my SPF record is missing or incorrect?

• Answer: Add or update your SPF record by specifying the IP addresses and mail servers authorized to send emails on your behalf. You can use an SPF checker tool to ensure it is correctly configured.

How do I configure DKIM for my domain?

• Answer: To configure DKIM, you need to generate a public-private key pair. The private key is used to sign outgoing emails, and the public key is added to your DNS as a DKIM record. Tools like this can help you validate your DKIM setup.

What is the best way to configure DMARC for my domain?

• Answer: Add a DMARC record to your DNS that specifies how email servers should handle emails that fail SPF or DKIM checks. It’s recommended to start with p=none (monitoring mode) and then move to p=reject stricter protection once you’ve confirmed the correct configurations.

How can I verify if my PTR record is configured correctly?

• Answer: Use a reverse DNS lookup tool to check if your PTR record matches your mail server’s domain name.

Why is my email marked as spam even though I have the correct DNS records?

• Answer: There could be other factors at play, such as your domain’s reputation, blacklisting, or low engagement rates. Ensure you maintain a positive sender reputation and follow email best practices.

What does it mean if I receive a DNS lookup limit exceeded error for SPF?

• Answer: SPF records can perform a maximum of 10 DNS lookups. If you exceed this limit, your SPF check will fail. Simplify your SPF record by consolidating mechanisms or reducing the number of included domains.

How long does it take for DNS changes to propagate?

• Answer:

DNS changes typically take between a few minutes to 48 hours to propagate worldwide. You can monitor the propagation progress using tools 

What should I do if DNS records are cached and causing delivery issues?

• Answer: Clear the DNS cache on both your local machine and email servers. You may also want to reduce the TTL values of your DNS records to ensure faster updates in the future.