IP Warming
Email MarketingAlso: IP Warm-up · Warming a Sending IP
Quick definition
IP warming is the process of gradually increasing email volume sent from a new IP address so that Internet Service Providers (ISPs) like Gmail and Outlook can build trust in it. Sending a huge volume immediately from an unproven IP looks like spam behaviour and triggers filtering.
How it varies across Australia
Australian senders migrating platforms or scaling volume typically underestimate how long warming takes. ISPs judge new IPs against engagement signals built up slowly, and rushing the ramp tends to cost more in deliverability than the time saved.
See email marketing benchmarks across Australian industries →What it actually means
Think of a new sending IP like a new tradesperson with no reviews. Turn up to ten jobs a day in week one and every customer treats you with suspicion. Start with one trusted client, do good work, let word spread, then take on more. IP warming applies that same logic to email infrastructure.
Mailbox providers like Gmail and Outlook track sender reputation per IP address. A brand-new IP has zero history, so a sudden spike in volume looks identical to a spammer's behaviour. The response is predictable: filtering to spam, throttling, or outright blocking.
Warming solves this by starting small, sending to your most engaged subscribers first, and increasing volume in steps over several weeks. Each successful send with strong open rate and low complaint rate builds trust with the ISP. Skip the ramp and you risk poisoning the IP's reputation before it has a chance to earn one, which then affects every subsequent campaign including transactional email.
This matters most when migrating email service providers, adding a new sending domain, or scaling volume sharply after a slow period.
An IP address has no reputation until you build one. Sending like you already have one is how you never get it.
How to calculate it
Warm-up = gradually increasing send volume from a new IP over 2-6 weeks
Worked example. Week one: send 500 emails to your most engaged segment. Week two: 2,000. Week three: 8,000. Week four: 25,000. By week six you're at full volume, assuming open rate stays healthy and complaint rate stays low at each step.
The Australian context
Australian senders often warm IPs against a mixed inbox landscape, Gmail and Outlook dominate but engagement patterns differ from US benchmarks because of smaller list sizes and tighter niche audiences. A slower, more conservative warming schedule tends to suit Australian sender volumes better than templates built for US-scale lists.
Where people get this wrong
Related terms
Common questions
How long does IP warming take?
Typically two to six weeks depending on target volume. Larger senders aiming for hundreds of thousands of emails per send need a longer, more gradual ramp than a business sending a few thousand.
Do I need to warm a shared IP?
No. Shared IPs already carry reputation from other senders using the same pool. Warming applies to dedicated IPs, which start with no sending history and need to build trust from scratch.
What happens if I skip IP warming?
Mailbox providers treat the sudden volume as suspicious and filter mail to spam or block it outright. Recovering a damaged reputation takes longer and is harder than warming properly the first time.
Which subscribers should I email first during warm-up?
Your most engaged segment, people who open and click regularly. Strong engagement signals early in the warm-up build reputation faster than mailing your full list including cold or inactive contacts.
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About New Rebellion
New Rebellion is a marketing intelligence consultancy. We build tools, score Australian businesses on how their marketing actually performs, and publish Debrief every day. This dictionary is part of how we work in the open.
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