KoltrixIP warm-up: a realistic schedule and what to watch daily
A practical IP warm-up plan that ramps volume over weeks, prioritizes engaged recipients and backs off on deferrals, with daily signals to check.
On this page(9 sections)
A new IP address has no reputation, and mailbox providers treat strangers with suspicion. Warm-up is the process of introducing the IP gradually, with mail recipients actually want, so receivers learn to trust it before you ask them to accept your full volume.
Why warm-up exists
Receivers protect their users by limiting how much mail they accept from sources they do not know. A brand-new IP that suddenly sends 200,000 messages looks exactly like a compromised server or a spammer who just rented infrastructure. The usual response is deferral (temporary 4xx errors), throttling, filtering to spam, or outright blocking.
If the same IP sends a few hundred messages on day one, to people who open them, and grows steadily, receivers see a pattern consistent with a legitimate sender. Each day's good results earn a bit more acceptance.
This applies to dedicated IPs you control. On a shared pool, your provider has already warmed the IPs.
Before you send anything
Warm-up goes faster when the basics are in place on day one:
- Reverse DNS: the IP has a PTR record under your domain that resolves back to the same IP.
- HELO name: the server introduces itself with that same hostname.
- SPF: the IP is authorized, directly or through your provider's include.
- DKIM: messages are signed with your domain.
- DMARC: a policy is published, with aggregate reporting enabled.
- Monitoring: you can see deferrals, bounces and complaints per receiving provider, daily.
- Your list: you know which recipients engaged recently, because they go first.
A realistic schedule
There is no official schedule, and providers publish only general guidance. The table below is a conservative starting point for an IP that will eventually carry around 100,000 messages a day. Treat the numbers as a shape, not a contract.
| Day | Daily volume on new IP | Audience |
|---|---|---|
| 1 | 200 | Most engaged (opened or clicked in the last 30 days) |
| 2 | 500 | Most engaged |
| 3 | 1,000 | Most engaged |
| 4 | 2,000 | Engaged in last 30 days |
| 5 | 4,000 | Engaged in last 30 days |
| 6 | 7,000 | Engaged in last 60 days |
| 7 | 10,000 | Engaged in last 60 days |
| 8 to 10 | 15,000 to 25,000 | Engaged in last 90 days |
| 11 to 14 | 30,000 to 50,000 | Engaged in last 90 days |
| 15 to 21 | 60,000 to 80,000 | Broader active list |
| 22 to 30 | Up to 100,000 | Full intended audience |
Two rules make the schedule work:
- Only advance when the previous day was clean. If deferrals or complaints rose, repeat the step or go back one.
- Send every day. Gaps reset some of the trust you built. If you must pause, resume at a lower step.
Transactional mail warms an IP well, because it is expected and opened. If you can route a slice of password resets and receipts through the new IP early on, it helps.
Splitting traffic during warm-up
You rarely get to stop sending while an IP warms. The usual approach is to keep your old infrastructure, a shared pool or older IPs, carrying the bulk of traffic, and shift a growing percentage to the new IP each day. Many sending systems support weighted routing for exactly this.
Route by receiving domain if you can. Each large mailbox provider builds its own view of your IP, so it helps to ramp at a similar rate across Gmail, Outlook.com, Yahoo and others, rather than accidentally sending all early volume to one of them.
What to watch daily
| Signal | Healthy | Slow down when |
|---|---|---|
| Deferral (4xx) rate per provider | Low and falling | Rising, or above a few percent at one provider |
| Hard bounce rate | Well under 1% | Rising; usually means old addresses slipped in |
| Spam complaints | Near zero | Any noticeable increase |
| Opens and clicks | Similar to your normal engaged rates | A sharp drop, possibly meaning spam-folder placement |
| Blocklist status | Not listed | Any listing |
| Postmaster dashboards | Stable or improving | Reputation dips |
Reading deferrals
Deferrals are the main way receivers tell you to slow down. Messages like these are common during warm-up:
421 4.7.0 Try again later, closing connection.
451 4.7.1 Temporarily deferred due to unexpected volume or user complaints.Exact wording varies by provider and changes over time. The meaning is the same: you are sending faster or more than this receiver currently accepts from your IP. Your MTA should retry with backoff, and your ramp should pause until deferrals settle.
Common mistakes
- Starting with the whole list. Old, unengaged addresses produce bounces, complaints and trap hits exactly when the IP is most fragile.
- Warming with a single big campaign. The first impression is a spike.
- Ignoring per-provider differences. One provider may accept your volume happily while another defers heavily.
- Pushing through deferrals. Retrying aggressively during deferrals makes things worse.
- Warming too many IPs at once. Each needs real volume. Splitting a small warm-up volume across several IPs slows them all.
- Stopping monitoring after day 30. Reputation keeps moving; warm-up is simply when it moves fastest.
When warm-up is going badly
If deferrals climb and stay high or mail starts going to spam at one provider:
- Drop back to the last volume that was clean.
- Narrow the audience to the most engaged recipients.
- Check authentication and reverse DNS again; a mistake there undermines everything else.
- Look at content and list source for the days that went badly.
- Resume the ramp more slowly once results stabilize.
Checklist
- PTR, HELO, SPF, DKIM and DMARC configured before day one.
- Engagement segments prepared, most engaged first.
- Weighted routing between old and new infrastructure.
- Daily volume roughly doubling early, then growing more slowly.
- Daily per-provider review of deferrals, bounces and complaints.
- A rule to repeat or step back after any bad day.
- Sending every day throughout the ramp.
Key takeaways
- Warm-up builds trust in a new IP by sending wanted mail in steadily increasing volume.
- Start with your most engaged recipients and widen the audience as volume grows.
- Deferrals are the receiver telling you to slow down; respect them.
- Advance only after clean days, send daily, and watch each major provider separately.
- Plan on roughly four weeks for a mid-volume IP, longer for larger volumes.
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