What is an IP warm-up?

IP warm-up is the process of gradually increasing send volume from a new or cold IP address so ISPs (Gmail, Outlook, Yahoo) learn the sender is legitimate. Skipping warm-up causes throttling and bulk-folder delivery.

How long does IP warm-up take?

Typically 4–6 weeks for most senders, longer for very large lists. The exact schedule depends on list size, send frequency, and content quality.

What is a Random Bucket Number (RBN)?

An RBN is a randomly assigned number (usually 0–99) on each user record. It lets you target 'RBN 0–5' on day 1, 'RBN 0–10' on day 2, and so on, giving you an evenly distributed, growing audience.

Should I include a holdout group during warm-up?

Yes. A holdout (typically 5–10%) that receives no sends during warm-up gives you a clean incremental-impact baseline once you go fully live.

What happens if I skip IP warm-up?

ISPs flag the high volume as suspicious. Emails land in spam or bulk, bounce rates spike, and recovery can take weeks.

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IP Warm-Up Planner

Name: Orbit
Availability: InStock
Author: Justin Williames

Build an incremental IP warming schedule with Random Bucket Numbers for Braze.

This tool is part of Orbit. A free Claude Desktop extension with 50+ lifecycle marketing skills. Pay what you think it's worth once it saves you a day.

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Target daily volumeWarm-up daysCurrent avg daily sends

Global Holdout Group

About the IP Warm-Up Planner

Free IP warm-up schedule generator for email senders. Builds a day-by-day ramp plan with Random Bucket Numbers (RBNs) for even audience distribution, plus optional holdout groups. Use it to warm a new dedicated IP, recover a reputation-damaged IP, or migrate between ESPs.

How to use

Enter your total sendable list size.
Set the warm-up duration (usually 4–6 weeks).
Set a starting volume (commonly 1,000–5,000 sends on day 1).
Optionally add a holdout group percentage.
Export the daily schedule with RBN ranges per send.

Common use cases

Warming a brand-new dedicated IP
ESP migration (new IPs need warming even with the same content)
Recovering an IP after a deliverability incident
Scaling send volume without triggering ISP throttling

Who it's for

Deliverability specialists, lifecycle marketers, and MarOps teams responsible for email sender reputation.

Frequently asked questions

What is an IP warm-up?: IP warm-up is the process of gradually increasing send volume from a new or cold IP address so ISPs (Gmail, Outlook, Yahoo) learn the sender is legitimate. Skipping warm-up causes throttling and bulk-folder delivery.
How long does IP warm-up take?: Typically 4–6 weeks for most senders, longer for very large lists. The exact schedule depends on list size, send frequency, and content quality.
What is a Random Bucket Number (RBN)?: An RBN is a randomly assigned number (usually 0–99) on each user record. It lets you target 'RBN 0–5' on day 1, 'RBN 0–10' on day 2, and so on, giving you an evenly distributed, growing audience.
Should I include a holdout group during warm-up?: Yes. A holdout (typically 5–10%) that receives no sends during warm-up gives you a clean incremental-impact baseline once you go fully live.
What happens if I skip IP warm-up?: ISPs flag the high volume as suspicious. Emails land in spam or bulk, bounce rates spike, and recovery can take weeks.

Related Orbit tools

Built into Orbit for Claude

Orbit runs your whole warm-up, not just the plan.

Inside Orbit for Claude, the Deliverability Management skill doesn't stop at a schedule. Claude builds the RBN segments in your Braze workspace, sets up the daily campaigns, monitors engagement and bounce thresholds day-by-day, and tells you when it's safe to ramp or when to pause.

Get Orbit Pay what it's worth