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
13 marketer 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.
21 Nov 2023 - 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.
7 Feb 2024 - Neil Patel's Blog
What the experts say
3 expert 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.
19 Apr 2024 - 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.
20 Jan 2025 - Email Geeks
What the documentation says
4 technical 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.
4 Nov 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.
28 Oct 2021 - Microsoft Learn
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