What DNS records are required to solve '450 4.1.8 Sender address rejected: Domain not found' errors?

Summary

The '450 4.1.8 Sender address rejected: Domain not found' error generally indicates a problem with DNS configuration, preventing recipient servers from verifying the sender's domain. To resolve this, it's crucial to ensure the correct setup and presence of several DNS records, including MX records (for directing incoming mail), A and AAAA records (for mapping the domain to an IP address), and SPF and DKIM records (for authenticating outgoing emails and preventing spoofing). Additionally, checking for proper forward-confirmed reverse DNS (FCrDNS) and allowing sufficient time for DNS propagation are important. Diagnostic tools can aid in identifying and correcting misconfigurations.

Key findings

  • DNS Record Deficiency: The primary cause is often a lack of or incorrect configuration of essential DNS records (MX, A/AAAA, SPF, DKIM).
  • MX Record Importance: Correct MX record setup is critical for directing incoming mail to the appropriate mail server.
  • Authentication Records (SPF/DKIM): SPF and DKIM are vital for authenticating outgoing emails, preventing them from being marked as spam or rejected.
  • Forward-Confirmed Reverse DNS (FCrDNS): Proper FCrDNS is necessary for SMTP to validate the legitimacy of the sending server.
  • DNS Diagnostic Tools: Various tools can be used to check and verify DNS configurations and identify potential issues.

Key considerations

  • 5321 From Domain Configuration: Ensure that A/AAAA/MX records are correctly configured for the 5321 From Domain.
  • Proper Hostname Setup: Verify that the hostname used for SMTP connections matches the configured A record.
  • DNS Propagation Time: Allow adequate time for DNS changes to propagate fully (up to 48 hours).
  • SPF Configuration Specifics: Ensure your SPF record includes all mail servers authorized to send emails on behalf of your domain.
  • Active Domain Registration: Confirm that your domain is properly registered and active.

What email marketers say
13Marketer opinions

The '450 4.1.8 Sender address rejected: Domain not found' error commonly arises from DNS misconfigurations that prevent recipient servers from verifying the sender's domain. Resolving this involves ensuring the presence and correct configuration of several DNS records, including MX records (to direct incoming mail), A and AAAA records (to map the domain to an IP address for sending), and SPF and DKIM records (to authenticate outgoing emails and prevent spoofing). Using DNS checking tools can help diagnose specific issues.

Key opinions

  • MX Records: Correct MX record configuration is essential for directing incoming email to the appropriate mail server.
  • A/AAAA Records: A records (and AAAA for IPv6) map the domain to an IP address, which is necessary for email sending.
  • SPF Records: SPF records authorize specific mail servers to send emails on behalf of your domain, preventing unauthorized use.
  • DKIM Records: DKIM records add a digital signature to emails, verifying the sender's authenticity and preventing tampering.
  • DNS Verification: Tools are available to check DNS records and ensure they are correctly configured and propagated.

Key considerations

  • 5321 From Domain: Ensure A/AAAA/MX records exist for the 5321 From Domain.
  • Record Alignment: Verify proper alignment of SPF and DKIM records for domain authentication.
  • Hostname Matching: Ensure the hostname used for SMTP connections matches the configured A record.
  • DNS Propagation: Allow sufficient time for DNS changes to propagate globally.
  • Regular Checks: Periodically review DNS settings and authentication protocols to maintain email deliverability.
Marketer view

Email marketer from Sendinblue explains that email authentication helps verify your identity and improves deliverability rates. You should set up SPF (Sender Policy Framework) to specify which mail servers are allowed to send emails on behalf of your domain and DKIM (DomainKeys Identified Mail) to add a digital signature to your emails. These measures help prevent your emails from being marked as spam.

October 2021 - Sendinblue
Marketer view

Email marketer from Neil Patel's Blog shares that to fix domain not found errors, focus on your DNS records. Ensure your MX records are correct so other mail servers know where to send emails for your domain. Also, set up SPF and DKIM records to authenticate your outgoing emails. These records help prove your emails are legitimate, reducing the chances of them being rejected.

May 2021 - Neil Patel's Blog
Marketer view

Email marketer from Namecheap explains that MX records route incoming emails to the mail server. An A record maps a domain name to an IP address. SPF records allow you to specify the mail servers and domains that are authorized to send emails on behalf of your domain. DKIM records add a digital signature to outgoing emails. If the records aren't set up correctly, email may be rejected.

October 2024 - Namecheap
Marketer view

Email marketer from Stackoverflow explains that you need to check if you have an A record setup for your subdomain you're using for your SMTP connection in your control panel. Also, make sure your hostname matches the one you're using for SMTP.

March 2021 - Stackoverflow
Marketer view

Email marketer from Hostinger explains that issues with email delivery can often be traced back to DNS settings. Confirm that your MX records are accurately configured to point to the correct mail servers. Additionally, make sure your SPF record lists all authorized sending sources for your domain. These checks help ensure that receiving servers recognize and accept your emails as legitimate.

May 2021 - Hostinger
Marketer view

Email marketer from Mailjet Support explains that the 'Domain not found' error often results from DNS misconfigurations. You should ensure your MX records are correctly pointing to Mailjet's servers, and set up SPF and DKIM records to authorize Mailjet to send emails on your behalf. Incorrect DNS settings can lead to deliverability issues, so it's crucial to configure them properly.

July 2024 - Mailjet
Marketer view

Email marketer from Email Geeks indicates the error might be due to a lack of A/AAAA/MX records for the 5321 From Domain.

July 2023 - Email Geeks
Marketer view

Email marketer from Email Geeks confirms that the 5321 From Domain has MX, SPF, and DKIM records but is missing A and AAAA records.

July 2023 - Email Geeks
Marketer view

Email marketer from Reddit explains that to fix domain not found errors ensure your domain is resolving by checking it with a public DNS tool such as Google Admin Toolbox Dig or similar. Also, check your domain's MX, SPF, and DKIM records using the same tool.

June 2021 - Reddit
Marketer view

Email marketer from DNSQueries explains that to diagnose a 'Domain not found' error, use an online DNS checker to verify the configuration of your MX records, A records, SPF records, and DKIM records. These tools will help you confirm whether the necessary DNS records are correctly set up and propagating properly, providing insights into potential misconfigurations.

May 2022 - DNSQueries
Marketer view

Email marketer from Litmus explains that one of the reasons you may see an issue with emails not sending is because of the 450 4.1.8 error. Usually caused by the lack of proper DNS records that prove the sender is authorized to send on behalf of your organization.

January 2024 - Litmus
Marketer view

Email marketer from cPanel suggests checking your SPF record. The SPF record is a DNS record that identifies which mail servers are authorized to send email on behalf of your domain. Make sure that your SPF record is properly configured and includes all of the mail servers that you use to send email.

December 2023 - cPanel
Marketer view

Email marketer from EasyDMARC explains that an SPF record permits sending emails through authorized mail servers only. This record helps in email authentication and prevents spam. The domain owner lists authorized IP addresses and hostnames to send emails on behalf of the domain through the SPF record.

June 2022 - EasyDMARC

What the experts say
3Expert opinions

The '450 4.1.8 Sender address rejected: Domain not found' error indicates a DNS-related issue affecting email deliverability. Troubleshooting involves verifying DNS records like A, MX, SPF, and DKIM to ensure proper configuration and authentication. Correctly setting up these records allows receiving servers to validate the sender's authorization and prevent email rejection.

Key opinions

  • DNS Error: The error message indicates a DNS error, requiring a thorough check of DNS records.
  • MX Records: Correct MX record configuration is crucial for directing incoming email to the correct mail server.
  • SPF Records: SPF records authorize specific mail servers to send emails on behalf of your domain, preventing unauthorized use.
  • Authentication: Setting up SPF and DKIM records is vital to authenticate emails and prevent rejection.

Key considerations

  • DNS Lookups: Perform DNS lookups (A and MX) for the domains in the 5321 and 5322 from addresses.
  • DNS Configuration: Ensure proper DNS configuration for email deliverability.
  • SPF Setup: Set up Sender Policy Framework (SPF) properly to authorize email providers.
Expert view

Expert from Spam Resource highlights that ensuring proper DNS configuration is crucial for email deliverability. Specifically, the '450 4.1.8' error often points to issues with missing or misconfigured MX records. These records tell other mail servers where to deliver email for your domain. Additionally, setting up SPF and DKIM records is vital to authenticate your emails, which can help prevent them from being rejected.

November 2022 - Spam Resource
Expert view

Expert from Email Geeks explains the error message indicates a DNS error. The troubleshooting strategy involves performing DNS lookups (A and MX) for the domains in the 5321 and 5322 from addresses to verify the authoritative servers have the correct records.

May 2022 - Email Geeks
Expert view

Expert from Word to the Wise answers question about setting up SPF records, explaining that setting up Sender Policy Framework (SPF) properly lets email providers know that you have authorized them to send emails on behalf of your domain.

October 2021 - Word to the Wise

What the documentation says
4Technical articles

The '450 4.1.8 Sender address rejected: Domain not found' error is commonly due to missing or misconfigured DNS records, preventing the recipient server from locating your domain's information. Key records to verify include MX (to direct incoming mail), A (to map hostname to IP), SPF and DKIM (to authenticate emails). Furthermore, ensure the domain is registered, DNS settings are correct (including forward-confirmed reverse DNS), and sufficient time has been allowed for DNS propagation.

Key findings

  • Missing/Incorrect DNS: The error indicates the recipient server couldn't find your domain's DNS records.
  • MX Records: MX records must be valid and point to your mail server (or Google's, if using Workspace).
  • A Record: An A record is needed to map your hostname to the correct IP address.
  • SPF and DKIM: SPF and DKIM records should be properly configured to authenticate your emails.
  • FCrDNS: SMTP requires forward-confirmed reverse DNS (FCrDNS) for legitimacy.

Key considerations

  • Domain Registration: Verify that your domain is properly registered and active.
  • DNS Settings: Check your DNS settings to ensure they are correct.
  • Propagation Time: Allow up to 48 hours for DNS records to propagate fully.
  • DNS Lookup Tools: Use online DNS lookup tools to check the visibility of your DNS records.
Technical article

Documentation from Digital Ocean explains that DNS records such as MX, A, SPF and DKIM records may not have propagated yet. DNS propagation can take up to 48 hours, though it usually completes much faster. Use online DNS lookup tools to check if your DNS records are visible globally.

December 2024 - Digital Ocean
Technical article

Documentation from Microsoft Learn explains that the '450 4.1.8 Sender address rejected: Domain not found' error usually means the recipient's email server couldn't find your domain's DNS records. This often means the domain either doesn't exist or the DNS settings are incorrect. Specifically, make sure you have valid MX records pointing to your mail server, an A record for your hostname, and ensure your SPF and DKIM records are properly configured to authenticate your emails.

March 2021 - Microsoft Learn
Technical article

Documentation from RFC5321 details that SMTP requires forward-confirmed reverse DNS (FCrDNS). This means the sending server's IP address must have a PTR record (reverse DNS) that resolves to a hostname, and that hostname must have an A record (forward DNS) that resolves back to the original IP address. This validation helps prevent spam and confirms the legitimacy of the sending server.

December 2023 - RFC5321
Technical article

Documentation from Google Workspace Admin Help details that to resolve the 'Domain not found' error, first verify that your domain is properly registered and active. Then, check your DNS settings. Ensure your MX records point to the correct Google mail servers (if using Google Workspace). Also, create SPF and DKIM records to authorize Google to send emails on behalf of your domain. This prevents your emails from being flagged as spam.

July 2021 - Google Workspace Admin Help