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Manage Sending IP Reputation and Handle TSS04 Deferrals

Manage Sending IP Reputation and Handle TSS04 Deferrals

This article explains how Paubox manages the IP addresses your email is sent from. It also covers what you can do to protect your sending reputation, and what to do when a provider such as Yahoo or AOL temporarily defers your mail with a TSS04 error.

Summary

  • Paubox manages the IP addresses your marketing email is sent from, including routing changes when a provider defers mail.
  • Dedicated IPs are available on request as a paid option. Contact Sales to discuss one.
  • Recipient providers such as Yahoo and AOL may temporarily defer mail with a 421 4.7.0 [TSS04] error when they see unexpected volume or complaints. The steps below help you reduce that risk.

How Paubox manages sending IPs

  • By default, your email is sent from IP addresses that Paubox manages. Paubox handles routing changes at the infrastructure level.
  • Dedicated IPs: if you'd like your email to be sent from an IP address of your own, dedicated IPs are available on request as a paid option. You can't set up a dedicated IP yourself in the Paubox dashboard. Contact Paubox Sales to discuss one.
  • One-off alternate IPs: sending a single message from a different IP address isn't available.
  • For real-time information about widespread issues, check the Paubox status page at status.paubox.com.

What a 421 4.7.0 [TSS04] deferral means
A 421 4.7.0 [TSS04] response means the recipient's provider, such as Yahoo or AOL, is temporarily deferring messages from the sending IP. Providers do this when they see unexpected sending volume or complaints from their users. It's a temporary block set by the recipient's provider, not a permanent rejection.

How to improve deliverability and protect your reputation

Set up sender authentication

  • Make sure your domain has correct SPF and DKIM DNS records. These records show providers that your messages really come from you, which helps keep them out of spam.

Protect your domain's reputation

  • Avoid sending mass mailings from domains you use for transactional or sensitive email.
  • Don't use purchased lists. Sending to people who don't know you or don't engage raises complaints and hurts your reputation.

Follow content best practices

  • Avoid attachments and links that commonly trigger spam filters.
  • Double-check recipient addresses for typos before you send.
  • Keep your content relevant and expected, so recipients are less likely to report it.

Ask key recipients for help

  • Ask important recipients to check their spam folder and mark your messages as "Not spam".
  • Ask them to add your sending address or domain to their safe senders list.

Be patient with temporary deferrals

  • Paubox automatically retries deferred messages for up to 24 hours, so you don't need to resend right away.
  • Deferrals like TSS04 are often temporary. Avoid resending the same email several times in a short period, because repeated attempts can make reputation signals worse.

When to contact Paubox Support

  • If delivery problems continue across several recipients or domains, contact Paubox Support. Include the affected domains or recipients and when the problem started, so our team can investigate.
  • To ask about a dedicated IP, contact Paubox Sales.

Conclusion
Good deliverability depends on both Paubox and you. Keep your SPF and DKIM records correct, avoid risky practices like purchased lists and unexpected mass sends, follow content best practices, and give temporary deferrals time to clear. If problems continue, contact Paubox Support with the affected domains and timing. If you'd like a dedicated IP, contact Paubox Sales.