SMTP code 421 4.7.0 TSS04
What the knowledge base's own tables say about this code, and which articles say it — a description of the reply, never a placement prediction.
- Provider
- Yahoo
- Response matched (regex, abridged)
- 421 4.7.0 [TSS04] (deferred, user complaints). The vendor file also has: any [TS?S04] leads to Suspend for 2 h, with no threshold
- Trigger
- 2/hr
- Action
- Suspend
- Duration
- 2 h
From Per-Provider Tuning Baselines · Automated-throttle rules per provider (community-contributed)