SMTP reference

Yahoo TS03: deferred for policy reasons

Yahooreputation_blockaction: pause

Yahoo's [TS03] tag marks a deferral for policy or reputation reasons. It arrives as a 4xx, so the message is still queued, but it is a reputation signal rather than a capacity one. Back off and look at your complaint rate.

A good example of why status-code class alone is a poor guide. This is a 4xx, which normally means retry, but the message text explicitly says retrying will fail. Bounce classification has to read the text.

What it looks like in the log

421 4.7.0 [TS03] All messages from x.x.x.x will be permanently deferred; Retrying will NOT succeed.

421 4.7.0 [TSS04] Messages from x.x.x.x temporarily deferred.

Why it happens

Complaint rate above what Yahoo tolerates.
Spam trap hits on Yahoo-operated domains.
A volume pattern Yahoo reads as unestablished or abusive.

What to do

Read the text, not just the code. "Will be permanently deferred; retrying will NOT succeed" means stop, despite the 4xx.
Enrol in Yahoo's complaint feedback loop and make sure complaints reach suppression.
Reduce volume to Yahoo domains and rebuild with engaged recipients only.

5.7.1 · 4.7.28

Classifying this automatically

This response maps to reputation_block with a recommended action of pause in smtpsift, an open-source classifier for SMTP rejections and deferrals.

Yahoo TS03: deferred for policy reasons

What it looks like in the log

Why it happens

What to do

Related

Classifying this automatically