Summary
When a new ESP blocks addresses previously delivered due to 'invalid domain' reasons, the issue commonly stems from stricter validation and authentication practices compared to the previous ESP. This can manifest as DNS configuration issues (particularly with MX records), more rigorous domain reputation checks, heightened IP reputation sensitivity, variations in list hygiene standards, more aggressive usage of suppression lists, and changes in how DNS is propagated. Contacting the new ESP's support team, validating DNS configuration, examining suppression lists, and warming up IPs appropriately are crucial troubleshooting steps.
Key findings
- Stricter Validation: New ESPs often employ more stringent validation of email addresses and domains, leading to blocks of addresses that the previous ESP accepted.
- DNS Configuration Issues: Incorrect or missing MX records, problems with DNS propagation, or temporary DNS lookup failures can cause the new ESP to reject domains.
- IP Reputation Sensitivity: New ESPs may be more sensitive to IP reputation, resulting in more aggressive blocking, especially during the initial IP warmup phase.
- Inconsistencies in List Hygiene: Variations in list cleaning practices between ESPs can result in addresses previously deemed valid now being flagged as invalid.
- Suppression Lists: The new ESP might have integrated with shared suppression lists or maintain internal lists where these addresses are present due to past bounces or complaints.
- Domain Reputation: New ESPs may perform more rigorous domain reputation checks and are less tolerant of domains with poor reputations or associations with spam.
- Potential ESP misclassification: The invalid domain reason provided by the ESP might be a misclassification, in which case communicating with the ESP to find more specific information might be useful
- From address MX record missing: The domain in the From address of the headers does not have an MX record which is being enforced by the new ESP but not the last ESP
Key considerations
- Contact ESP Support: Reach out to the new ESP's support team to gain specific insights into why addresses are being blocked and to review relevant logs.
- Verify DNS Configuration: Carefully review the DNS configuration of both sending and receiving domains, paying particular attention to MX records, SPF records, and DKIM setup.
- Check Suppression Lists: Examine suppression lists within the new ESP to determine if the blocked addresses are present.
- IP Warmup: Implement or refine the IP warmup process to establish a positive sending reputation with the new ESP.
- Enhance List Hygiene Practices: Re-evaluate and potentially improve list cleaning practices to meet the stricter standards of the new ESP.
- Consider DNS Propagation: Keep in mind DNS propagation delays, as changes to DNS records may not be immediately reflected across all servers.
- ESP Validation: Discuss acceptable deliverability accuracy with your new ESP, if you want to deliver email to addresses that dont have valid configurations (like missing MX records or similar)
What email marketers say
11 marketer opinions
A new ESP blocking addresses previously delivered by another ESP due to 'invalid domain' reasons can stem from a multitude of factors. These include stricter validation processes, differences in DNS propagation and caching, more aggressive blacklist usage, variations in IP reputation handling, and the potential for list hygiene discrepancies. Contacting the ESP support, examining suppression lists, and verifying DNS configurations are crucial troubleshooting steps.
Key opinions
- Validation Differences: New ESPs often have more stringent validation processes, which may flag domains previously accepted by a less strict ESP.
- DNS Issues: DNS propagation delays or temporary DNS lookup failures can cause a new ESP, using different DNS servers or having stricter timeouts, to block domains intermittently.
- IP Reputation: New ESPs may be more sensitive to IP reputation, leading to aggressive blocking, especially during IP warmup phases.
- List Hygiene: Inconsistencies in list cleaning practices can result in addresses being considered invalid due to stricter hygiene standards at the new ESP.
- MX Record Issues: The new ESP may be enforcing checks for MX records in the 'From' address of the headers, which were not enforced previously.
- Suppression Lists: Addresses could be on the new ESP's suppression list either due to a shared list or historic bounces/complaints on the previous ESP.
- New or Young Domains: The new ESP may be more strict about new or young domains due to the likelihood of them being used for spam
- ESP Accuracy: The previous ESP may have inaccurately reported deliveries.
Key considerations
- Contact ESP Support: Reach out to the new ESP's support team for specific insights into why the domains are being blocked and to review logs.
- Check Suppression Lists: Verify if the blocked domains are present on any suppression lists within the new ESP.
- Review DNS Configuration: Ensure proper DNS configuration, including MX records, and consider potential DNS propagation delays.
- IP Warmup Strategy: Implement a proper IP warmup strategy to build a positive reputation with the new ESP.
- List Hygiene Practices: Re-evaluate and potentially enhance list cleaning practices to align with the new ESP's requirements.
- ESP Validation: Discuss acceptable deliverability accuracy with your new ESP, if you want to deliver email to addresses that dont have valid configurations (like missing MX records or similar)
Marketer view
Email marketer from Quora responds that the new ESP may be more sensitive due to a lack of IP reputation. Even with dedicated IPs, a warmup process is required. The new ESP could be blocking more aggressively to avoid being flagged as a spam source early on.
8 Jul 2022 - Quora
Marketer view
Email marketer from LinkedIn recommends that it's possible that the domains were previously suppressed due to bounces or complaints on the previous ESP and that the new ESP has integrated with a shared suppression list. Check if the domains are on any suppression lists within the new ESP.
31 May 2024 - LinkedIn
What the experts say
6 expert opinions
When a new ESP blocks addresses previously delivered due to an 'invalid domain' reason, it often points to stricter validation practices, potential misclassifications, or domain-related issues. Experts suggest that the new ESP might have problems validating MX records, be conducting rigorous domain reputation checks, or have stricter standards for list hygiene. Investigating whether the recipient MX rejected the message and communicating with the ESP is vital to addressing the issue.
Key opinions
- Stricter Validation: New ESPs may have stricter standards than previous ones for validating domains and email addresses, leading to more blocks.
- MX Record Validation: The new ESP might be experiencing problems validating MX records, or the records themselves could be misconfigured or missing, leading to a block.
- Misclassification: The 'invalid domain' reason could be a misclassification by the ESP, requiring direct communication to understand their practices.
- Domain Reputation: A new ESP may perform more rigorous domain reputation checks, leading to the flagging of domains previously accepted if their reputation has declined.
- List Hygiene Standards: New ESPs might enforce higher standards for list hygiene, causing addresses to be blocked that were previously accepted by an ESP with more lenient processes.
Key considerations
- ESP Communication: Contact the new ESP to understand the specific reasons behind the 'invalid domain' blocks and their validation processes.
- Investigate MX Rejection: Determine if the recipient's MX server rejected the email, and understand the specific error message.
- Check Domain Reputation: Evaluate the domain's reputation to ensure it hasn't been associated with spam or low engagement.
- Verify MX Records: Ensure proper MX record configuration for both the sending and receiving domains.
- Review List Hygiene: Evaluate and improve list hygiene practices to meet the new ESP's more stringent requirements.
Expert view
Expert from Spam Resource explains that a new ESP is likely performing more rigorous domain reputation checks. Domains previously accepted might now be flagged because of changes to their reputation (e.g., becoming associated with spam or low engagement). The previous ESP may not have had these checks in place or may have had different thresholds.
31 May 2024 - Spam Resource
Expert view
Expert from Word to the Wise emphasizes that a new ESP might have stricter standards for list hygiene. This can lead to addresses being blocked that the previous ESP accepted, as they may have had more lenient validation or hygiene processes.
10 Jan 2023 - Word to the Wise
What the documentation says
5 technical articles
Documentation indicates that a new ESP blocking addresses due to 'invalid domain' errors often stems from DNS configuration issues, stricter validation of MX records, and potential problems with email authentication protocols like SPF and DKIM. These issues might not have been apparent with the previous ESP due to different retry policies, caching mechanisms, or less stringent enforcement of authentication standards.
Key findings
- DNS Configuration: 'Invalid domain' errors can occur if recipient domain's DNS records (e.g., MX records) are improperly configured, unreachable, or experiencing DNS server issues.
- MX Record Validation: New ESPs might enforce stricter validation of MX records, causing them to block domains that lack explicit MX records or have improperly configured ones.
- Authentication Protocols: Incorrect SPF records or improper DKIM setup can cause domain blocks as new ESPs do more thorough checks and stricter enforcement of email authentication protocols.
- DNS Resolution Issues: The receiving mail server might be unable to resolve the domain name in the recipient's email address, indicating a temporary DNS issue or a genuinely invalid domain.
- ESP Differences: Previous ESPs may have had different retry policies or DNS caching mechanisms that masked these intermittent DNS resolution issues.
Key considerations
- Check DNS Records: Verify the DNS records of the recipient domains, particularly the MX records, to ensure they are correctly configured and reachable.
- SPF and DKIM Setup: Ensure proper setup and configuration of SPF and DKIM to enhance email authentication and improve deliverability.
- Troubleshoot DNS Resolution: Investigate and resolve any DNS resolution issues that may be affecting the recipient domains.
- ESP Communication: Contact the new ESP to understand their specific validation and authentication requirements.
- Monitor Delivery: Monitor email delivery to identify and address any ongoing DNS-related or authentication-related issues.
Technical article
Documentation from AWS specifies that incorrect SPF records could be the reason for domain blocks. The new ESP might do more thorough SPF checks than the old, and incorrect configurations lead to sending failures.
12 Apr 2023 - AWS
Technical article
Documentation from Mailjet states that a 'domain does not exist' error indicates the receiving mail server could not resolve the domain name in the recipient's email address. This is different from a mailbox not existing; the domain itself is the problem. This can be a temporary DNS issue, or the domain may genuinely be invalid. Previous ESPs may have bypassed this with retries, or older data.
7 Jun 2022 - Mailjet
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