Proactive throttling means deliberately capping send rates to stay within ISP limits.
Best practices:
- 📊 Segment sends by receiving domain
- 📦 Split databases into batches
- ⚙️ Use MTA-level controls (messages/minute)
- 📆 Maintain consistent daily volume
Watch for 421 soft bounces — ISPs explicitly asking you to slow down.
Gmail prefers consistent, predictable volume. Microsoft treats outlook.com, hotmail.com, and msn.com as the same servers.
🔴 Avoid: Alternating between massive sends and silence.
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