What is “IP temporarily blocked”?

IP temporarily blocked indicates reputation-based throttling:

What it means:

Your sending IP has triggered defensive measures. The block is temporary and will lift after a period. Different from permanent blocklisting.

Common triggers:

Volume spike: Unusual increase in sending. Complaint spike: Elevated spam reports. Bounce rate: High invalid addresses. Suspicious patterns: Behavior resembling spam.

Typical codes:

421 with "temporarily blocked" or "try again later." 4.7.0 (temporary authentication failure due to IP reputation).

Response:

Wait for the block to lift (hours to days). Reduce sending volume. Investigate what triggered the block. Review list hygiene and sending practices.

Temporary IP blocking is a timeout. Cool off, and access will be restored.