How to know if your IP is being rate-limited or throttled?

Rate limiting and throttling manifest through several observable symptoms.

4xx SMTP responses indicating temporary deferrals, often with messages like "too many connections" or "try again later." Slow delivery speeds where messages sit in queues longer than normal. Delayed inbox placement where delivered mail arrives hours after sending.

Your ESP's sending dashboard typically shows queue depths and deferral rates. Providers like Gmail and Microsoft return specific error codes when they are throttling an IP.

Gmail Postmaster Tools shows delivery errors that can indicate throttling. Microsoft SNDS traffic light indicators turning yellow or red suggest reduced trust.

Throttling is the harbor master telling your ship to wait at anchor. You are not banned, but you are not welcome to dock at full speed until trust improves.

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