How to resolve 550 5.7.1 email blocklist errors when sending from 17hats?

Key findings

1. Shared ip address: The 550 5.7.1 error from 17hats, particularly with low individual sending volume, points to a block on a shared IP address. This means other users on the same IP are likely responsible for the poor reputation that led to the block.
2. Esp responsibility: When using a shared IP, it is the responsibility of the Email Service Provider (ESP), in this case 17hats, to manage the IP's reputation and address any blocklistings. They should have internal systems to identify and mitigate problematic senders.
3. Network reputation: The specific IPs mentioned, such as those associated with eigbox.net (part of Endurance, which includes iPage and Netfirms), are often linked to poor sending practices or problematic traffic, leading to frequent blocklistings.
4. Recurring issue: If the IP address changes but the blocklisting persists, it suggests the underlying issue (e.g., the ESP's network practices) has not been resolved. Some hosts may rotate IPs instead of fixing the root cause.
5. Authentication not enough: Even with correct SPF and DKIM authentication, an email can be blocked if the sending IP address has a poor reputation. The domain's authentication status does not override an IP blocklist.

Key considerations

1. Contact 17hats: As the issue is on a shared IP, 17hats is the primary party that needs to resolve the block with Microsoft or the respective blocklist operator. Push them to take action.
2. Verify sending path: Confirm whether 17hats always uses the problematic network (like eigbox.net) or if there's a setting in your 17hats account that allows you to configure a different SMTP smart host. If you've connected your own web host's email, that could be the source.
3. Evaluate alternatives: If 17hats cannot resolve the recurring blocklist issues, consider migrating to a different Email Service Provider with a strong focus on deliverability and reliable IP reputation. This might involve moving to a provider with better IP reputation management.
4. Microsoft delisting: While 17hats should handle it, familiarise yourself with the Microsoft delisting form and troubleshooting page for reference. However, direct submission might be less effective if the IP is shared and repeatedly abused.

Key opinions

1. Esp's responsibility: Marketers frequently state that if an ESP uses shared IPs, it is their duty to manage the reputation of those IPs and address any blocklistings. The individual sender cannot fix a shared IP issue directly.
2. Shared ip challenges: Low sending volume does not guarantee immunity from deliverability problems when on a shared IP, as the actions of other users can still lead to blocklistings for everyone on that IP.
3. Impact of poor infrastructure: Some ESPs or underlying hosting providers have historically poor email sending reputations, leading to recurring issues. Marketers often advise moving away from such providers if problems persist.
4. Delisting process: While users can submit delisting requests, marketers find them less effective for shared IPs unless the ESP takes corrective action against the problematic senders on their network.

Key considerations

1. Escalate to esp support: If you are experiencing blockages from a shared IP, consistently escalate the issue with your ESP's support team. Provide them with the bounce messages and request they investigate and remediate the IP's reputation. This is critical for resolving IP blocks.
2. Assess long-term viability: If an ESP's shared IP strategy consistently leads to deliverability problems, it may be time to consider migrating to an ESP with a stronger reputation and proactive deliverability management.
3. Understand authentication: While SPF and DKIM might pass, a block at the IP level indicates the recipient server is rejecting the connection before checking domain-level authentication. Understanding how these records work is still important for overall deliverability.

Key opinions

1. Problematic host: Experts identify eigbox.net as a network with a consistently poor reputation, often associated with providers like iPage or Endurance. They suggest this is a significant part of the problem.
2. Ip rotation strategy: Some hosting companies are known to rotate IPs as they get blocklisted rather than implementing effective spam prevention and reputation management, perpetuating deliverability issues.
3. Sending path analysis: It's crucial to determine if 17hats inherently uses these problematic networks for all its customers or if the user has configured their 17hats account to relay through a web host that uses such networks. The solution differs based on this distinction. Understanding the sending path is key to diagnosing blocklist issues.
4. PTR records: The presence of eigbox.net in the PTR records of the sending system indicates that emails are indeed originating from that network, regardless of the user's specific web host.

Key considerations

1. Direct versus configured sending: Ascertain if 17hats defaults to sending via eigbox.net or if the user configured 17hats to use their web host (which happens to be eigbox.net). This distinction dictates the remedial steps.
2. Review smart host settings: If 17hats allows for SMTP smart host configuration, check if the user has inadvertently pointed it to a service with a poor reputation. If so, removing this configuration could resolve the issue.
3. Provider diligence: Experts advise that using providers (ESPs or web hosts for email) known for poor reputation management or IP rotation without addressing the root cause will lead to ongoing deliverability challenges. Selecting a reputable ESP is paramount for consistent inbox placement.
4. Understanding bounces: Thoroughly analyzing bounce messages, including the reporting MTA and specific error codes (like Microsoft S3150), provides critical clues about the exact nature and source of the block.

Key findings

1. Error meaning: The 550 5.7.1 error is a common SMTP bounce code indicating a permanent failure, often due to the sender being blocked by the recipient's email system because of policy reasons, such as being on a blocklist.
2. Microsoft s3150: Microsoft's specific S3150 code (as referenced in the bounce) usually indicates that the sending IP address or network has been identified as compromised or sending spam, leading to a block.
3. Ip reputation focus: Even if SPF and DKIM are correctly configured, an email can be rejected if the IP address itself has a poor reputation, as IP-based blocklists operate at an earlier stage of the email delivery process.
4. Delisting process: Most major email providers (like Microsoft) offer specific forms or processes for requesting IP delisting. However, these often require the IP owner (the ESP) to submit the request and demonstrate remediation of the underlying issues.

Key considerations

1. Sender best practices: Documentation consistently advises senders to adhere to email best practices, even if they're using an ESP. This includes maintaining clean mailing lists, sending relevant content, and avoiding spam traps.
2. Esp communication: Official resources often guide users to contact their Email Service Provider first for deliverability issues, especially when shared IPs are involved. The ESP is typically better equipped to interact with postmasters and blocklist operators. This is key for resolving Microsoft email blocks.
3. Authentication standards: While not the primary cause of an IP block, maintaining proper SPF, DKIM, and DMARC configurations (as outlined in email authentication guides) is crucial for overall sender reputation and to prevent other deliverability issues.
4. Persistent problems: If blocks recur even after delisting requests, it indicates a systemic issue with the sending infrastructure that requires a more fundamental change, such as moving to a more reputable ESP or obtaining a dedicated IP if volume permits.