Terra troubleshooting support

Sending successfully to Terra and reaching the inbox is highly dependent on your sending reputation and following sending best practices. While following best practices doesn’t guarantee inbox placement at Terra, it greatly increases your chances for success. 

One of the best ways to reach the inbox at Terra, is sending relevant content that your subscribers want to receive. Low complaint rates and having subscribers marking your email as “not spam” signals to Terra that you are less likely a spammer.

Troubleshooting tips 

  • Check your SMTP logs for clues regarding the issue.
    • Terra blocks email with its own realtime block list. If your email is being throttled or blocked, check your SMTP logs for a response indicating a possible cause.
    • Common error for volume limits: 421 4.7.0 Error: too many errors" received from ( while connected from (
    • Submit a request to lift the block after you have identified and fixed the cause.
  • Terra is very sensitive to high complaint rates. Ensure all IP addresses are signed up with their complaint feedback loop and that all complainers are immediately added to a suppression list.
  • Terra uses the Cloudmark spam filter. Spammy fingerprints on your content from Cloudmark are usually the result of high complaints and sending to spam traps. Ensure you are following list acquisition and list hygiene best practices to reduce the likelihood your email is perceived as spam.
    • Submit an IP reputation reset request to Cloudmark once you have identified and fixed the cause. If you don't fix the cause, listings at Cloudmark are likely to recur.
  • Check your Sender Policy Framework (SPF) record and ensure it contains all of the sending IP addresses used in sending bulk email to Terra. A failed SPF verification typically results in a block. The SPF check for Terra is not present in the Authentication-Results: header, but Terra confirms the use of SPF on their postmaster website. Check that SPF is working correctly using another mailbox provider such as Gmail or Outlook (Hotmail) or by using an SPF validation tool.
  • Ensure DKIM is passing authentication verification by checking the Authentication-Results: header in one of the Terra CoreSeeds. You should see "dkim=pass".
  • Exceeding a 10% unknown user rate usually results in a temporary block at Terra. The block may last several hours, allowing you to address the problem and resume sending. But, consistently exceeding the 10% unknown user rate will result in further blocks.
  • If you receive feedback from subscribers or see SMTP bounces indicating a delay in messages received, contact your Email Service Provider (ESP) and make sure your email is being sent according to all SMTP sending specifications. Specifically, Terra insists all IP addresses have a reverse DNS record.
    • Some Email Service Providers do not meet all of the technical requirements for sending email. A percentage of connections from those servers may be de-prioritized, leading to some messages being delayed.
  • Check your system to ensure that spam was not sent from an unauthorized sender.
    • Ensure your system is not acting as an open relay.
    • Ensure the content you are sending does not contain viruses or malware.
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