SMTP code 421 IPTS04
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.
The knowledge base documents this code in more than one row. What tells those rows apart is the rejection text in your own log, not the code: read each line below against what your rejection says.
- Provider
- Yahoo
- Response matched (regex, abridged)
- 421 [IPTS04]
- Trigger
- 2/hr
- Action
- Suspend
- Duration
- 2 h
From Per-Provider Tuning Baselines · Automated-throttle rules per provider (community-contributed)
- Provider
- Yahoo Japan
- Response matched (regex, abridged)
- 421 [TSS04] or 421 [IPTS04] (volume or complaints)
- Trigger
- 2/hr
- Action
- Suspend
- Duration
- 1 h
From Per-Provider Tuning Baselines · Automated-throttle rules per provider (community-contributed)