VEmail Deliverability Glossary

Volume Spike

A sudden large increase in sending volume that deviates from your established pattern. ISPs flag these as suspicious behavior matching spam botnets.

A volume spike is a sudden, significant increase in email sending volume that deviates from your established sending pattern.

Why volume spikes damage deliverability:

ISPs monitor sending patterns over time and build an "expected behavior" model for each sender. A sudden 10× volume increase is a red flag that matches the behavior of compromised accounts and spam botnet operators.

Safe volume growth rule: Increase volume by no more than 20–30% per week during warm-up. For established senders, avoid more than a 2–3× increase from your typical volume within a single day.

Planned seasonal spikes (e.g., Black Friday): Even for legitimate seasonal increases, warm up to your anticipated peak volume gradually in the weeks leading up to the event, rather than going from normal volume to 10× overnight.

Frequently Asked Questions

What counts as a volume spike that could harm deliverability?

A harmful volume spike is typically defined as sending more than 2–3x your average daily volume in a single day, or increasing weekly volume by more than 30–50% without a gradual ramp. For a sender who has been averaging 1,000 emails/day, sending 5,000 on a single day is a spike that ISPs will flag. For a sender averaging 10,000/day, sending 30,000 on a single day crosses the spike threshold. The relative increase matters more than the absolute number — ISPs compare each day's volume to your established historical pattern, not to some fixed universal threshold.

How should I handle planned high-volume events like Black Friday?

Begin ramping toward your Black Friday volume 3–4 weeks before the event. If you normally send 10,000/day and need 100,000 for Black Friday, increase gradually: week one to 20,000/day, week two to 40,000/day, week three to 70,000/day, then 100,000 on the day. This establishes a new baseline before the event, so the actual campaign volume doesn't look like a spike relative to your recent history. Also ensure your warm-up tool is running at higher engagement levels throughout this pre-event period to support the reputation needed for the increased volume.

What should I do if I accidentally sent a volume spike?

Stop sending immediately once you realize the spike has occurred. Check Postmaster Tools and your sending metrics for the next 24–48 hours — did your inbox placement rate drop? Did complaint rates rise? If metrics remain stable, the spike may not have caused lasting damage; resume normal volume carefully. If metrics declined, reduce to 50% of your normal volume for a week and monitor for recovery before gradually rebuilding. In severe cases (large spike from a new or low-reputation sender), you may see blacklisting or significant reputation drops that require a full warm-up restart at minimal volume.

Related Terms

Email Volume Ramp-Up

The planned, gradual increase in sending volume during warm-up — giving ISPs time to observe positive behavior before large volumes are introduced.

Ramp-Up Schedule

The specific plan of increasing daily send volume over time during warm-up. See Email Volume Ramp-Up for a full example schedule and principles.

IP Reputation

The trust score ISPs assign to a specific sending IP based on bounce rates, complaint rates, spam trap hits, and sending pattern consistency.

Domain Reputation

The permanent trust score ISPs assign to your sending domain based on historical behavior. Unlike IP reputation, a damaged domain reputation can take months to recover.

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