Definition
Send velocity smoothing is the practice of distributing a large email send over a longer period, injecting mail at a measured, consistent rate rather than pushing the entire volume out at once. It keeps sending within infrastructure and provider limits and avoids the sudden bursts that can look unusual.
Rather than firing 500,000 emails as fast as possible, a smoothed send might drip the queue out over several hours, respecting per-hour and per-domain limits set by the sending platform.
Why Smoothing Matters
| Reason | Effect |
|---|---|
| Avoids rate limits | Stays within per-hour and per-domain caps |
| Protects reputation | Consistent sending reads as more trustworthy than erratic bursts |
| Avoids sharp peaks | Reduces strain on infrastructure and recipient providers |
| Spreads delivery | Messages reach recipients over a window, evening out load |
Smoothing is especially important for warm-up, large blasts and new IPs.
When to Smooth Sends
- Very large campaigns: Very high volumes risk throttling without smoothing.
- New IPs or domains: Gradual ramp protects unproven reputation.
- High-frequency sends: Multiple bursts need pacing.
- Cold or riskier audiences: Slower, measured sending is safer.
How to Smooth a Send
- Set a per-hour cap: Cap how many messages send each hour.
- Stagger the start: Introduce the send gradually rather than all at once.
- Respect per-domain limits: Since a provider limits that domain, pace its share.
- Use connection and job throttling: Configure the platform to drip the queue.
- Monitor live feedback: Watch complaints and bounces as delivery proceeds.
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Frequently Asked Questions
Send velocity smoothing is spreading a large email send over time at a controlled rate rather than sending it all at once, keeping delivery within limits and avoiding disruptive bursts.
Smoothing avoids hitting rate limits, protects sender reputation by avoiding erratic bursts, and keeps delivery steady and predictable. It is especially important for very large campaigns, new IPs and warm-up phases.
Consistent, measured sending is easier on reputation and infrastructure than sudden, high-volume bursts, which can look suspicious and trigger throttling. Smoothing keeps each domain and provider within comfortable limits.
Cap your messages per hour, stagger the start of large sends, respect per-domain limits, and configure your platform's connection and job throttles to drip the queue. Monitor complaints and bounces live to catch problems early.