Docs Error Library Email Delivery Errors Error 421-4.7.0 Unsolicited Mail and Rate Limiting

Error 421-4.7.0 Unsolicited Mail and Rate Limiting

What Is Causing This Error?

‘Error 421-4.7.0’ is triggered when an email provider, like Gmail, detects a high volume of unsolicited mail coming from your IP address. This detection leads to a temporary rate limitation on emails sent from the IP, as a measure to protect users from potential spam.

Common reasons for this error include sending large volumes of emails in a short period, which may be perceived as spam, or if your IP has been previously flagged for sending unsolicited emails.

Resolving the Error – Solution

To effectively handle SMTP Error 421-4.7.0:

  1. Moderate Email Volume: Limit the number of emails sent in a short period to avoid spam-like behavior.
  2. Ensure Content Compliance: Review your email content to ensure it aligns with best practices and avoids being marked as spam.
  3. Authenticate Emails: Set up SPF, DKIM, and DMARC records to authenticate your emails. For more details, check out Google’s guide on configuring DKIM and SPF authentication.
  4. Monitor IP Reputation: Use services like Google Postmaster to track and improve your domain’s reputation.
  5. Understand Rate Limiting: Familiarize yourself with the concept and causes of rate limiting to better manage email activities.

That’s it! Now you know the common causes of the ‘421-4.7.0’ error and how to resolve it.

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