How to Warm Up an Email: Day-by-Day Schedule

An email warmup schedule for cold email has three phases. Days 0 to 2: set up the domain, authentication and mailboxes. Days 1 to 14: warmup only, no cold email. Days 14 to 21: cold email starts low and rises to up to 25 a day per mailbox, with warmup still running. Each step up in volume waits until three checks pass: authentication, a stable warmup inbox rate and a placement test for Google and Outlook recipients.

We make Outreach2day, cold email infrastructure with warmup included in every mailbox. The schedule below is the one we recommend to our users. If you only need the short answer on duration, read how long to warm up a new mailbox. This post is the plan: what happens on which day, and what to check before moving on. To pick the software that runs the warmup, see best email warmup tools; for what a warmup service does and costs, see email warmup service.

The Schedule at a Glance

Day 0 is the day you buy or connect the domain. Cold volume is per mailbox per day and does not include warmup emails.

The 5, 10, 15, 20 figures are an example ramp. The rule is: nothing cold before day 14, a low start on day 14, and up to 25 cold emails per mailbox per day by around day 21. Any ramp that rises in small steps between those points fits the plan.

Warmup Volume per Day

On Outreach2day, each mailbox sends 25+ warmup emails a day to Google recipients, 25 to Outlook recipients and 25 to other providers, so 75+ warmup emails a day in total. That runs on every mailbox and is included in the $2.50 per mailbox per month.

If you run warmup in a separate tool, start at the tool's low setting and let it ramp according to its own settings. Don't copy numbers from a different tool: warmup networks differ in size and in how they count emails. Two rules hold for any tool:

• Keep the daily level steady once it reaches its target. Change it in small steps over several days.

• Don't push warmup up to fix a bad rate. A sudden jump in volume is what Google's guidelines warn against (quoted below and in the section on failed checks).

Google's sender guidelines describe the same principle for any new sender: "Start with a low sending volume to engaged users, and slowly increase the volume over time," and "Send email at a consistent rate. Avoid sending email in bursts."

How to Warm Up a New Email Domain, Step by Step

1. Set up the domain on day 0. Buy a separate domain for cold email or connect one you own. Add SPF, DKIM and DMARC records (on Outreach2day they are set up automatically). If you connect your own domain, the nameserver change takes 24 to 48 hours.

2. Create the mailboxes. Up to 5 mailboxes per domain. New Outreach2day mailboxes are ready within 24 hours.

3. Verify authentication before warmup starts. Send a test message and confirm SPF, DKIM and DMARC pass. You can look up the records with the SPF, DKIM and DMARC checker. Warmup started before DNS has propagated can fail quietly.

4. Run warmup only for at least 14 days. No cold email from the mailbox in this period. Check on day 1 or 2 that warmup emails are going out and coming back; a mailbox shown as connected is not enough.

5. Run the gate check on day 13. Authentication passes, the warmup inbox rate has been stable for several days, and a placement test lands in the inbox for both Google and Outlook recipients.

6. Start cold email low on day 14. Send a small number per mailbox, spread across the working day.

7. Raise cold volume in steps until day 21. Repeat the gate check before each step. Reach up to 25 cold emails per mailbox per day around day 21.

8. Keep warmup running after day 21. Warmup stays on for as long as the mailbox sends cold email. See why to keep warmup running while sending.

The Checks Before Each Step

Run these before the first cold email and again before each increase:

A warmup inbox rate is an early warning signal: warmup partners have a history with your mailbox and your prospects don't. That's why the placement test is a separate check. For how to run one and read the result, see are inbox placement tests reliable.

What to Do When a Check Fails

Hold. Don't raise cold volume, and don't skip the step and come back to it later.

1. Keep cold volume where it was on the affected mailboxes, or set it back to the previous step.

2. Keep warmup running at its normal level.

3. Find which layer failed. One mailbox, one domain, or every domain on the same sending IPs. See what a warmup inbox rate drop means.

4. Re-run the check after a few days. Move to the next step only when it passes.

Google's guidance for the same situation: "If messages start bouncing or start being deferred, reduce the sending volume until the SMTP error rate decreases. Then, increase slowly again." It also warns that "immediately doubling previously sent volumes suddenly could result in rate limiting or reputation drops" (sender guidelines).

A held schedule takes longer. Cheaper extensions such as .info can need more time before full volume. Day 21 is the earliest day for full volume.

Scaling Schedule: Adding Mailboxes

Every new mailbox needs the full schedule, including mailboxes that replace a burned domain. Plan capacity three weeks ahead: buy and warm the extra domains and mailboxes 21 days before you need them to send at full volume.

Example: you send from 20 mailboxes on 4 domains today (up to 500 cold emails a day at 25 each) and want 1,000 a day.

The arithmetic: 1,000 ÷ 25 = 40 mailboxes, and 40 ÷ 5 = 8 domains. The cold email capacity calculator does this for other volumes. Follow-ups count toward the same 25 a day per mailbox; the cold email follow-up sequence post shows how a sequence multiplies sends.

If you add a large batch, stagger it: warm and ramp a few domains at a time, so total volume rises in steps rather than at once. The per-mailbox ceiling stays at 25 no matter how many mailboxes you run; see cold emails per mailbox per day.

IP Warmup Is a Different Schedule

IP warmup applies when you send through an email service provider on a dedicated IP address: the IP itself has no history, so you raise the volume sent from it over weeks. Amazon SES says a positive reputation takes "around two weeks" with some mailbox providers and "up to six weeks" with others, and its automatic warmup for standard dedicated IPs increases "over 45 days" (Amazon SES documentation). The schedule in this post is for mailboxes on your own domains: it warms the domain and the mailbox, and does not involve leasing or warming an IP.

FAQ

Can I send cold email during the first 14 days?

No. Keep the mailbox on warmup only for at least 14 days. Sending cold email earlier puts strangers' spam complaints and non-replies on a mailbox with no history.

Do I warm up the domain or each mailbox?

Both, in practice. A new domain has no reputation and each mailbox on it has no sending history, so every new mailbox runs the full schedule, even on a domain that already has warmed mailboxes.

How many warmup emails should a mailbox send per day?

On Outreach2day, 25+ to Google recipients, 25 to Outlook and 25 to other providers, so 75+ a day. In a separate warmup tool, start at its low setting and follow its ramp.

Can I speed up the warmup schedule?

Not safely. Raising warmup or cold volume faster than the schedule is the abrupt change that Google's guidelines warn against, and a failed check adds more days than it saves.

When should I stop warmup?

Don't stop it while the mailbox sends cold email. Its inbox and spam rate are the earliest sign that a mailbox or domain is slipping.

Sources

Checked September 2026:

• Google: Email sender guidelines: start with low volume and increase slowly, send at a consistent rate, avoid sudden spikes and doubling volume, reduce volume when messages bounce or are deferred and increase slowly again.

• Amazon SES: Warming up dedicated IP addresses (standard): IP warmup takes around two weeks to up to six weeks depending on the provider; SES automatic warmup increases over 45 days.

Every Outreach2day mailbox comes with automatic SPF, DKIM and DMARC setup and warmup that keeps running while you send, for $2.50 a month (pricing; how that compares with other vendors: best cold email infrastructure providers).