Warmup (IP/Domain)
Warmup is the practice of gradually increasing email volume from a new IP address or sending domain over several weeks, so mailbox providers can build positive reputation for it. Sending high volume from cold infrastructure looks like spam and gets blocked. Warmup builds a believable history instead, and it comes in two flavours: IP warmup and domain warmup.
- Two kinds: IP warmup builds an address’s reputation, domain warmup builds your brand’s
- A new domain or dedicated IP starts with no history and must be ramped, not blasted
- Domain reputation is portable across IPs, so domain warmup almost always applies
- Lead with engaged recipients and grow volume gradually, watching provider signals
What warmup is, and its two forms
Reputation is earned, not granted. New email infrastructure has no track record, and mailbox providers treat unknown senders with suspicion because that is exactly how spammers operate: stand up fresh infrastructure, blast it, and discard it. Warmup sidesteps that by building a positive history on purpose, starting with a small daily volume to engaged recipients and increasing it on a steady curve over weeks.
Warmup comes in two forms, and serious senders do both. IP warmup builds the reputation of a specific sending IP address; it matters only on a dedicated IP, since a shared IP is kept warm by the whole pool. Domain warmup builds the reputation of your sending domain, which travels with your brand across every IP and provider. Because domain reputation is portable and increasingly the heavier signal, domain warmup applies in nearly every launch, even on shared IPs.
IP warmup vs domain warmup
The two are easy to confuse because you usually do them together, but they build different, separately tracked reputations:
- IP warmup establishes trust for the numeric address you send from. Skip it and a cold dedicated IP gets throttled; it is unnecessary on a shared IP.
- Domain warmup establishes trust for the domain in your
From:and DKIM signature. It is needed whenever the sending domain is new or has little history, regardless of which IP you use.
The practical takeaway: if you are on a shared IP you only need domain warmup; if you are on a new dedicated IP you need both. Either way, the reputation you build at the domain level persists even if you later change IPs, which is why the domain is the asset worth protecting most.
How a warmup runs
The mechanics are the same for both: start small, grow gradually (a common conservative rule is no more than about a 50% increase day over day), and send to your most engaged recipients first so early signals are strongly positive. A typical domain warmup spans 2 to 4 weeks and a dedicated-IP warmup 4 to 8 weeks. A simple combined ramp looks like this:
Week 1 50 to 500 per day, most-engaged segment
Week 2 1,000 to 5,000 per day
Week 3 10,000 to 20,000 per day
Week 4 scale toward full volume
Throughout: send daily, hold if complaints or throttling riseGetting warmup right
- Authenticate before the first send. Aligned SPF, DKIM, and a published DMARC record are prerequisites, not afterthoughts.
- Lead with engagement. Your openers and clickers produce the positive signals that build reputation fastest. Save cold or stale addresses for later, if at all.
- Be reactive, not rigid. Warm up per provider and watch complaints, bounces, and throttling. Hold or slow the ramp when signals sour rather than pushing the next step.
- Send consistently. Daily, predictable volume teaches providers you are a steady sender; long gaps undo progress.
- Keep the list clean. Practise list hygiene so you are not warming up by mailing dead addresses or spam traps.
A combined warmup ramp
IP warmup vs domain warmup
| IP warmup | Domain warmup | |
|---|---|---|
| Builds reputation for | A specific sending IP | Your sending domain |
| Needed when | New or dormant dedicated IP | New or low-history domain |
| Needed on a shared IP? | No | Yes |
| Typical length | 4 to 8 weeks | 2 to 4 weeks |
| Reputation travels? | No, stays with the IP | Yes, follows the brand |