# Warmup Email: The Exact Process We Use Across 32,000+ Inboxes

*Published: August 13, 2026*

A tactical, numbers-first guide to warming up a new email inbox before cold outreach, including tool comparisons, ramp schedules, and deliverability benchmarks.

--- A warmup email is an automated (or manual) message sent to gradually build a new inbox's sending reputation before you launch cold outreach. At BuzzLead, we run outbound across 32,000+ sending accounts, and the honest call is this: skip the warmup phase and you'll hit spam folders within days, regardless of how good your copy is. New inboxes need 3–4 weeks of low-volume, high-engagement sending before they can handle cold email at scale. Here's exactly how to do it right.

## What Does a Warmup Email Actually Do?

Email providers — Gmail, Outlook, and the ESPs behind them — score every sending domain and inbox based on behavioral signals: reply rates, spam complaints, bounce rates, and engagement patterns. A brand-new inbox with zero history looks suspicious the moment it sends 200 emails on day one.

A warmup email works by mimicking organic human behavior. Warmup tools send small volumes of emails between real (or simulated) inboxes, and those inboxes reply, open, and move messages out of spam. This trains the inbox's reputation upward before any prospect ever sees your name.

The practical result: a properly warmed inbox lands in primary tabs. A cold, unwarmed inbox lands in spam — or gets the domain blacklisted entirely.

## How Long Does Email Warmup Take?

For a brand-new domain and inbox, plan for **21–28 days minimum**. Here's the volume ramp we use at BuzzLead before handing an inbox to a client campaign:

Day Range

Daily Send Volume

Notes

Days 1–7

5–10 emails/day

Warmup tool only, no cold outreach

Days 8–14

15–25 emails/day

Warmup continues, monitor spam placement

Days 15–21

30–40 emails/day

Begin soft outreach (warm leads only)

Days 22–28

40–50 emails/day

Cold outreach can start at low volume

Day 29+

50–80 emails/day

Full campaign volume (never exceed 100/day per inbox)

The ceiling matters as much as the ramp. Across the 32k+ inboxes we manage, accounts that exceed 100 cold emails per day per inbox see a measurable spike in spam placement rates — even on aged, well-warmed domains. Keep it under that threshold permanently, not just during warmup.

## Which Warmup Tools Are Worth Using?

There are three tools we see most often in the wild, plus one approach that still works for low-volume senders. For a deeper comparison of sending platforms and their warmup capabilities, check out our [cold email outreach platform buyer's guide](https://buzzlead.io/blogs/cold-email-outreach-platform-the-buyers-guide-that-prioritizes-deliverability-20).

Tool

Best For

Warmup Network Size

Integrated Sending?

Price (approx.)

**Instantly.ai**

Agencies running high inbox volume

Large (500k+ accounts)

Yes (built-in sender)

From $37/mo

**Warmup Inbox**

Standalone warmup on any ESP

Mid-size

No (connects via SMTP)

From $15/inbox/mo

**Mailwarm**

Solopreneurs, small teams

Smaller

No

From $49/mo

**Lemwarm (Lemlist)**

Lemlist users

Mid-size

Yes (Lemlist only)

Bundled with Lemlist

**Manual warmup**

Very low volume, budget-constrained

N/A

N/A

Free

**Bottom line:** If you're running more than 5 inboxes, Instantly.ai's integrated warmup-plus-sending infrastructure is the most operationally efficient choice. For standalone warmup on inboxes you're sending from elsewhere (Smartlead, Outreach, etc.), Warmup Inbox connects cleanly via SMTP and doesn't require you to change your sending stack. We've also reviewed the [best email warmup services available in 2026](https://buzzlead.io/blogs/best-email-warmup-services-2026-the-definitive-tactical-guide) if you want a more comprehensive comparison.

## What Settings Should You Use Inside a Warmup Tool?

Most warmup tools expose the same core settings. Here's what to configure — and what to leave alone.

**Reply rate:** Set to 30–40%. This is the percentage of warmup emails that get a reply. Higher reply rates signal strong engagement to inbox providers. Don't drop below 25%.

**Spam rescue:** Enable this. When warmup emails land in your spam folder, the tool automatically moves them to the inbox and marks them as "not spam." This is one of the highest-leverage signals you can send to Gmail and Outlook.

**Daily ramp:** Most tools have an auto-ramp feature. Use it. Manual daily increases are fine, but the auto-ramp ensures you don't accidentally spike volume over a weekend.

**Warmup email content:** Leave it on the tool's default. The content of warmup emails is irrelevant — providers score behavior, not copy. Changing warmup content to match your brand is a waste of time.

**One setting to ignore:** "Warmup score" or "reputation score" displayed inside the tool. These are proprietary metrics that don't map directly to Google Postmaster or Microsoft SNDS data. Use those native dashboards to track actual deliverability health.

### 📥 Best Email Warmup Tools

The 6 warmup tools that work — ranked by an agency managing 20,000+ inboxes.

**[Get it here →](https://buzzlead.io/best/best-email-warmup-tools)**

## What Else Affects Deliverability Beyond the Warmup Email?

Warmup is necessary but not sufficient. The inboxes we manage that consistently hit primary tabs share five characteristics beyond a completed warmup. For a complete breakdown of inbox placement strategy, see our [email warmup complete guide to inbox placement in 2026](https://buzzlead.io/blogs/email-warmup-complete-guide).

- **Domain age and DNS configuration** — SPF, DKIM, and DMARC records must be set correctly before warmup starts. A misconfigured DKIM record will tank deliverability regardless of warmup duration.

- **Sending domain separation** — Never warm up or send cold email from your primary company domain. Use aged secondary domains (e.g., `getbuzzlead.io` instead of `buzzlead.io`). If that domain gets blacklisted, your core brand is protected.

- **List hygiene before launch** — Run every prospect list through a verification tool (ZeroBounce, NeverBounce, or Millionverifier) before sending. Bounce rate above 2% will damage a freshly warmed inbox faster than anything else.

- **Unsubscribe handling** — Include a plain-text unsubscribe option in every cold email. Spam complaints — not unsubscribes — are what destroy sender reputation.

- **Ongoing warmup during campaigns** — Don't turn off warmup once you start sending. Keep warmup running at 20–30 emails/day in the background throughout your campaign. It acts as a continuous reputation buffer.

## How Do You Know the Warmup Worked?

Don't guess. Test with a tool like **GlockApps** or **MailReach's spam test** before launching your first campaign sequence. Send a test email to their seed list and check where it lands — primary inbox, promotions tab, or spam — across Gmail, Outlook, and Apple Mail.

A properly warmed inbox should land in primary for Gmail and Outlook at a rate above 85% before you start cold outreach. If you're below that threshold, extend the warmup by another 7–10 days and retest. For the exact process we use to achieve 45%+ open rates, check out our [detailed email warmup methodology](https://buzzlead.io/blogs/email-warmup-the-exact-process-we-use-to-hit-45-open-rates).

Also monitor **Google Postmaster Tools** throughout the warmup period. Watch the Domain Reputation and IP Reputation charts. You want to see the reputation indicator move from "Low" to "Medium" or "High" before going live. If it stays at "Low" after 21 days, something is wrong with your DNS setup or your warmup tool's network quality.

## Frequently Asked Questions

**How many emails should I send per day during warmup?** Start at 5–10 emails per day in the first week and increase by 5–10 emails every 3–4 days. Never exceed 50 emails per day during the warmup phase itself. Once warmup is complete, cap cold outreach at 80–100 emails per day per inbox to protect long-term deliverability.

**Can I use a warmup email tool on a Gmail or Google Workspace account?** Yes. Most tools — Instantly, Warmup Inbox, Mailwarm — connect via SMTP/IMAP and work with Google Workspace, Outlook/Microsoft 365, and custom SMTP setups. Google Workspace is the most common setup for cold email because it has stronger deliverability than free Gmail accounts.

**Do I need to keep warmup running after I start sending campaigns?** Yes. Turn warmup off and your sender reputation slowly degrades, especially if campaign volume is high. Keep warmup running at 20–30 emails per day as a background reputation buffer throughout the life of the inbox.

**How long does a warmed inbox stay warm if I stop sending?** An inbox that goes completely dormant for 60+ days loses a significant portion of its warmup benefit. If you pause campaigns for more than 4 weeks, run a light warmup cycle (1–2 weeks at low volume) before restarting outreach.

**What's the difference between warming up a domain vs. warming up an inbox?** Domain reputation and inbox (IP) reputation are tracked separately by providers. Warming up the inbox builds inbox-level signals. Domain reputation is built through consistent, complaint-free sending over time. Both matter — which is why DNS configuration (SPF, DKIM, DMARC) must be correct from day one, not added after warmup starts.

If you'd rather not manage warmup infrastructure yourself, BuzzLead handles the full cold email stack — domain setup, warmup, list building, and campaign management — for B2B teams that need qualified meetings without the operational overhead. See how we work at [buzzlead.io](https://buzzlead.io).

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Source: https://buzzlead.io/blogs/warmup-email-the-exact-process-we-use-across-32000-inboxes