How do “burst sends” differ from throttled batches?
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Your campaign is ready. You've got 50,000 addresses queued up. Do you release them all at once or spread them over a few hours? That choice, between a burst send and a throttled batch, has real consequences for your inbox placement.
A burst send fires all messages as fast as your sending infrastructure can push them. For senders with strong, established reputations on well-warmed IPs, bursts can work fine. The recipient servers recognize the sender, trust the reputation, and process the flood. But for anyone with a newer IP, recovering reputation, or sending to a cold list, bursting the full volume at once is risky. Sudden volume spikes from a single IP look like spam behavior. Filters notice.
Throttled batches pace delivery deliberately, spreading messages over minutes or hours. Most ESPs do this automatically, staggering sends to avoid hitting any single provider's rate limits. Self-hosted setups on a mail transfer agent need this configured manually via concurrency limits and rate delays. Done well, throttling is nearly invisible to recipients but dramatically reduces deferrals and rate limit responses.
The right approach depends on your situation. If you're in IP warmup, throttled batches aren't just better, they're required. If you're a high-volume sender with years of clean history on dedicated IPs, controlled bursts may be fine. When in doubt, throttle. You can always speed up later; recovering from a reputation hit takes longer.
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