Email Warmup · Updated March 2026 · 12 min read

Email Warmup Guide 2026: How to Warm Up a New Email Account

Sending cold emails from a brand-new email account without warming it up is one of the fastest ways to destroy your sender reputation. Email providers expect new accounts to behave like real humans — starting with low volume, building gradually, and generating engagement. An account that goes from zero to 100 emails on day one looks exactly like a spam operation, because that's exactly what spam operations do.

This guide covers the complete email warmup process for 2026: what it is, why it matters, how to do it properly, and whether you need a warmup tool.

What Is Email Warmup?

Email warmup is the process of gradually establishing a sending reputation for a new email account. You start by sending a small number of emails per day, increasing volume slowly over 2–4 weeks, while ensuring those emails generate positive engagement signals (opens, replies, and moves out of spam).

The goal is to train email providers — primarily Google and Microsoft — that your account belongs to a legitimate sender who receives genuine engagement, not a spam account that blasts unengaged recipients.

Why Warmup Matters More in 2026

Google and Microsoft have significantly tightened their filters in the past two years. In February 2024, Google introduced mandatory authentication requirements and tighter spam rate thresholds for bulk senders. Microsoft made similar moves. The result: a new account sending cold email at volume without proper warmup gets flagged faster than ever.

The good news: if you warm up properly, maintain good list hygiene, and stay within volume limits, cold email deliverability is still very achievable.

Before You Start Warming Up

Warmup only works if your infrastructure is set up correctly first. Before sending a single warmup email:

• Configure SPF, DKIM, and DMARC on your sending domain. See our DNS authentication setup guide.
• Use a dedicated sending domain — not your main company domain. See cold email domain setup.
• Enable IMAP access on the new account (required for most warmup tools to work).
• Set up a professional email signature with your real name, title, and website.
• Add a Google Workspace or Microsoft 365 account rather than a free Gmail/Outlook account — custom domain addresses have higher deliverability baseline.

The Warmup Schedule: Week by Week

Here's a proven warmup schedule for a new Google Workspace or Microsoft 365 account:

These are conservative numbers. Some accounts can ramp faster. The key signal to watch: if your emails start landing in spam during the ramp, slow down and investigate before pushing volume higher.

Warmup Best Practices

Ensure Positive Engagement

The most important warmup activity isn't the number of emails you send — it's the engagement those emails generate. Email providers learn from user behavior. Emails that get opened, replied to, and moved from spam to inbox signal positive reputation.

During warmup:

• Send emails to real people who will actually open and reply
• If using a warmup service, make sure it's generating real opens and replies (not just sends)
• Move any warmup emails that land in spam back to the inbox manually for the first few weeks

Keep Content Natural

Warmup emails should read like real emails. Generic "this is a warmup email" messages with no context are fine for automated warmup tools — they're not meant to be read. But for the real emails you send during the ramp period, write naturally. Short, personal, relevant.

Vary Your Sending Times

Humans don't send emails at exactly 9:00:00 AM every day. Randomize your send times within a business hours window. Most email tools and warmup services do this automatically.

Don't Send Attachments or Multiple Links During Warmup

These are spam signals even for established accounts. Avoid them entirely during the warmup period.

Should You Use a Warmup Tool?

Warmup tools work by connecting your email account to a network of other email accounts and automatically sending/receiving emails between them, simulating organic engagement.

They're useful when:

• You're warming up multiple accounts at once (saves significant manual effort)
• You don't have enough real contacts to generate organic warmup volume
• You want to maintain warmup in the background while running cold campaigns

Popular warmup tools in 2026: Instantly (built-in warmup), Lemwarm, Warmbox, Mailreach. Most charge $15–$30/account/month.

The limitation: warmup tools generate artificial engagement. They're a useful supplement to real warmup but shouldn't be the only engagement signal your account generates. Combine warmup tool activity with real outreach to real humans during the ramp period.

Maintaining Email Health After Warmup

Warmup isn't a one-time event. Maintaining good deliverability requires ongoing practices:

• Keep volume steady. Don't suddenly jump from 40 to 200 emails/day — that spike looks like spam.
• Monitor bounce rate weekly. If it starts creeping up, clean your list before sending more.
• Check Google Postmaster Tools monthly. It shows your domain reputation for Gmail recipients.
• Run warmup tool continuously. Many teams leave warmup tools running in the background even after reaching full volume — it provides a consistent positive engagement signal that offsets any negative signals from cold email.
• Rotate accounts if reputation degrades. If one account starts showing deliverability issues, pause it and add a fresh account to the rotation.

Managing Multiple Sending Accounts

Most cold email operations at any scale need multiple email accounts to achieve the volume they need while staying within per-account limits. Here's the standard setup:

• 1 main sending domain + 2–3 variant domains (e.g., company.com, getcompany.com, trycompany.com)
• 2–3 email accounts per domain
• 40–50 emails per account per day
• = 200–450 cold emails/day across the infrastructure

Suplex manages this multi-account sending natively. It distributes volume across your accounts, monitors per-account limits, and handles the sending infrastructure — so you're focused on leads and messaging, not managing spreadsheets of sending accounts.

For the full picture of getting cold emails to the inbox, read our guide on why emails go to spam and how to fix it. To set up your domains and DNS properly, see the SPF/DKIM/DMARC guide.

Manual Warmup vs. Automated Warmup: Which Is Better?

The honest answer: manual warmup — actually sending real emails to real humans who reply — generates better reputation signals than automated warmup tools. Real human engagement is what email providers measure. Automated warmup creates artificial engagement in a network of connected accounts, which is valuable but not equivalent to organic engagement.

That said, manual warmup at scale is impractical. If you're warming up 5–10 accounts simultaneously, you can't manually generate 50–100 real human interactions per day across all of them. Automated warmup tools fill that gap.

Best practice: combine both. Do as much real-email warmup as is practical (forward interesting articles to colleagues, have genuine email conversations, use the account for actual work emails). Supplement with a warmup tool to hit volume targets. The combination is more effective than either approach alone.

Warmup for Google Workspace vs. Microsoft 365

The warmup experience differs slightly between providers:

Google Workspace: Generally more sensitive to volume spikes. The first 2 weeks are critical — keep volume very low and ensure engagement is high. Google's spam filters learn quickly from behavior patterns in those early days. The good news: once established, Google Workspace accounts have excellent deliverability when maintained properly.

Microsoft 365: Slightly more forgiving of volume ramp, but has its own Sender Reputation Service (SRS) that's independent of Google's filters. Accounts that warm up well for Gmail may still need additional warming for Outlook deliverability. Test inbox placement with Outlook-addressed test sends separately from Gmail.

If your target audience primarily uses Microsoft email (common in enterprise, government, and large corporations), prioritize warming up for Outlook specifically.

Signs Your Warmup Is Working

During the warmup period, watch for these positive indicators:

• Warmup emails landing in primary inbox (not spam or promotions) on test accounts you control
• mail-tester.com score of 8+/10
• Google Postmaster Tools showing "Medium" reputation moving toward "Good"
• Zero or near-zero bounce rate on test sends to verified addresses
• No blacklist entries on MXToolbox

Signs warmup isn't working (slow down and investigate):

• Test emails landing in spam or promotions
• mail-tester.com score below 7
• High bounce rate even on verified addresses
• Domain appearing on any blocklist