Yahoo Mail 421 4.7.0 [TS02]: complaint rate deferral.

Mail is paused because Yahoo is seeing a spike in spam complaints.

How to fix 421 4.7.0 [TS02].

Retrying or final
Retrying
A 4xx reply. Your server keeps the message queued and tries again.
Who is at fault
Sender
Your authentication, reputation, content, or sending pace.
Severity
WarningTemporary Deferral
Temporary421 4.7.0 [TS02]

TS02 reflects a trust downgrade driven by recent complaint or unsubscribe activity. Yahoo slows delivery so recipients are not overwhelmed.

Next steps

  1. 1Suppress unengaged contacts who have not opened in the past 90 days.
  2. 2Verify list acquisition sources and drop any third-party data.
  3. 3Highlight the unsubscribe link and confirm it works within one click.
  4. 4Pause campaigns that triggered the spike until reputation rebounds.
Yahoo Mail documentationEvery raw SMTP 421 reply

The same code at other providers.

Providers word the same code differently. Their fixes differ too.

421 4.7.0GmailTemporary system problemRetrying
421 4.7.0Microsoft 365 / OutlookTemporary system problemRetrying
421 4.7.0SFRToo many errorsRetrying

More Yahoo Mail codes.

Full Yahoo Mail playbook

Other Yahoo Mail fixes

421 4.7.0 [TS01]New or cold IP throttleRetrying
421 4.7.0 [TSS04]Temporary deferralRetrying
421 4.7.0 [TS03]Reputation holdRetrying
451Unresolvable from domainRetrying
554Unresolvable from domainFinal
554Unresolvable return pathFinal

In the glossary

Bounce (Soft)A soft bounce is when an email fails to deliver for a temporary reason, like a full inbox or a short outage at the recipient mail server. The address is still valid, and the email may be delivered if you try again later.
DeferralA deferral is when a receiving email server temporarily refuses a message but suggests trying again later.
ThrottlingThrottling is when inbox providers or your email platform slow or limit how many emails you can send in a set time. It acts like a speed limit so big sends do not overwhelm their systems or hurt your reputation.
GreylistingGreylisting is an anti-spam technique where a receiving server temporarily rejects emails from unknown senders to test if they are legitimate.

Browse all raw Yahoo Inc replies →

More references.

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