How to Warm Up an Email Address: The 2026 Practitioner's Playbook

You just launched a fresh domain, connected Google Workspace, and fired off your first 200-email sequence. By Thursday, 55% of those emails are sitting in spam - and your sender reputation is already damaged. That's not a worst-case scenario. That's the default outcome when you skip warmup.

Deliverability in 2026 is brutal. Office365 inbox placement dropped 26.7 percentage points year-over-year. Gmail started rejecting non-compliant emails at the SMTP level in late 2025 - not routing to spam, flat-out bouncing them. Some Gmail senders reported delivery rates as low as 12% in early 2026. If you're wondering how to warm up an email address without getting torched, this is the playbook.

Most guides stop at the schedule. This one covers the infrastructure, the data quality layer, and the maintenance discipline that separates teams hitting 10%+ reply rates from the 3.43% average.

What You Need (Quick Version)

Short on time? Here's the entire warmup process in five rules:

1. Set up SPF, DKIM, and DMARC before anything else. Non-negotiable. Fully authenticated senders are 2.7x more likely to reach inboxes.
2. Start at 5-10 emails per day and ramp over 8-12 weeks for brand-new domains. Existing domains with no outbound history need 3-6 weeks.
3. Manual warmup edges out automated - 93.7% vs. 91.3% inbox placement at week four. Use automated only if you're managing 3+ domains.
4. Never cold email from your primary domain. Always use dedicated secondary domains.
5. Verify your prospect list before sending your first real campaign. One batch with a 10%+ bounce rate undoes weeks of warmup.

That's the skeleton. The rest of this guide is the muscle and connective tissue.

What Email Warmup Actually Is

Email warmup is the process of gradually increasing your sending volume from a new (or dormant) email address to build a positive sender reputation with inbox providers like Gmail and Microsoft.

The mechanism isn't just volume - it's engagement signals. When recipients open your emails, reply, mark them as important, or spend time reading them, inbox providers learn that your messages are wanted. Over time, this pattern of positive engagement tells Gmail and Outlook to route your emails to the primary inbox instead of spam. Skip this process, and providers assume the worst. New accounts with no sending history get treated like potential spammers by default.

Step Zero - DNS Authentication (SPF, DKIM, DMARC)

Before you send a single warmup email, your DNS records need to be airtight. Google and Yahoo mandated SPF/DKIM/DMARC for bulk senders in February 2024. Microsoft followed in May 2025. Authentication isn't a best practice anymore - it's a requirement. 98% of spam filters check authentication records before evaluating anything else.

Get this wrong and nothing downstream matters.

After auditing hundreds of cold email setups, we see the same DNS mistakes over and over. Here's how to avoid them.

Set Up SPF

SPF (Sender Policy Framework) tells inbox providers which servers are authorized to send email on behalf of your domain. You're adding a TXT record to your DNS.

For cold email, use -all (hard fail). This tells receiving servers to reject anything not from your authorized senders. The softer ~all is for testing only - don't leave it in production.

Here's what catches people: SPF has a hard limit of 10 DNS lookups. Exceed it and the entire record breaks - providers treat it as if you have no SPF at all. Every include: statement counts as a lookup.

Common includes you'll need:

• Google Workspace: include:_spf.google.com
• Microsoft 365: include:spf.protection.outlook.com
• Instantly: include:_spf.instantly.ai
• Smartlead: include:_spf.smartlead.ai

Merge everything into a single SPF record. Multiple SPF records on the same domain is one of the most common mistakes I see - and it silently breaks authentication.

Set Up DKIM

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to your outgoing emails, proving they haven't been tampered with in transit.

Use 2048-bit keys. The older 1024-bit standard is weaker and increasingly flagged. Each sending service needs its own unique DKIM selector - a common mistake is setting up DKIM for Google Workspace but forgetting your cold email tool. Rotate your keys yearly. It's a 10-minute task that prevents long-term key compromise.

Set Up DMARC

DMARC ties SPF and DKIM together and tells inbox providers what to do when authentication fails. Here's the progression:

• Weeks 1-4: p=none (monitor only - collect reports, don't enforce)
• Weeks 5-8: p=quarantine (failed emails go to spam)
• Week 9+: p=reject (failed emails get blocked entirely)

Don't jump straight to p=reject. You need the monitoring phase to catch misconfigurations before they start bouncing legitimate emails. Only 7.6% of domains enforce DMARC with quarantine or reject policies. Getting this right puts you ahead of 92% of senders before you've sent a single campaign email.

Verify Your Setup

Send a test email to a Gmail account. Click the three dots, then "Show Original." You're looking for three green PASS results: SPF: PASS, DKIM: PASS, DMARC: PASS.

For a quick baseline score, use mail-tester.com - send an email to their generated address and get a deliverability score within seconds. It's free and catches the obvious problems.

DNS propagation takes 24-48 hours. Don't panic if your records don't show up immediately. But do verify before starting warmup - misconfigured DNS is the single most common cause of poor deliverability.

How Long Does It Take to Warm Up an Email Address?

The timeline depends entirely on your starting point:

New domains face roughly a 30-percentage-point inbox placement penalty compared to mature domains - 55% vs. 85% inbox placement out of the gate. That gap is what warmup closes.

One myth worth killing: domain age alone doesn't help. A 10-year-old domain that's never sent outbound email needs warmup just like a domain you registered yesterday. Inbox providers evaluate sending behavior, not registration dates. I've seen teams assume their aged domain gave them a head start, only to land in spam on day one because they skipped the ramp.

Building Your Email Warmup Plan: The Step-by-Step Schedule

Manual Warmup (Week-by-Week)

Manual warmup means sending real emails to real people who'll actually engage with them. It produces the best results - 93.7% inbox placement at week four - but requires effort and a network of responsive contacts.

If you aren't on Google Workspace or Microsoft 365, cap at 50/day. Lesser providers have tighter sending limits and less tolerance for volume spikes.

First-week rules are strict:

• Plain text only. No HTML templates.
• No images, no logos, no attachments.
• No links, no CTAs, no tracking pixels.
• No shortened URLs.

These restrictions exist because spam filters weight the first emails from a new sender heavily. A plain-text email that gets a reply looks like a real conversation. An HTML email with tracking pixels and three links looks like marketing - or worse, phishing.

You'll need 50-100 responsive contacts per domain. These are people who'll actually open and reply - colleagues, friends, other founders, your team. Ask them to reply with a sentence or two, not just "ok." Engagement depth matters: Gmail now weights time-to-read, reply length, and conversation threading.

One tip most guides miss: Sign up for a few reputable newsletters and SaaS free trials with your new email address. This creates inbound engagement signals - subscription confirmations, welcome sequences, product updates - that help establish legitimacy with inbox providers before you've sent a single outbound email.

Here's the thing: the hardest part of manual warmup isn't the schedule. It's finding enough people who'll reliably respond every day for four weeks. That's why most teams managing multiple domains switch to automated tools.

Automated Warmup Settings

Automated warmup tools handle the engagement loop for you - they send emails between real inboxes in their network, generating opens, replies, and positive signals automatically.

Here's the recommended configuration based on what we've seen work across dozens of setups:

• Starting volume: 10-15 emails/day per inbox
• Ramp rate: Increase 10-20% when health signals are green
• Daily cap: 30 emails per inbox maximum
• Reply rate setting: 30%
• Schedule: Business days only (Mon-Fri)

The critical rule: scale by adding warmed inboxes, not by spiking volume on a single sender. If you need to send 150 cold emails/day, that's five warmed inboxes at 30/day each - not one inbox at 150.

For high-volume senders (100K+/month): Start with 100% synthetic/seed traffic in week one, then mix in real traffic starting week two. Seed emails should make up at least 5% of total volume throughout the ramp. This staged approach prevents the sudden engagement drop that tanks reputation when you switch from warmup to real sends.

Keep warmup running continuously, even after you start real campaigns. The days of "warm up once, then stop" are over - Gmail weights ongoing engagement patterns, not just historical ones.

One caveat: Google banned automated warmup services in early 2023 for violating their terms of service. Most tools still work with Google Workspace accounts, but the risk of account suspension is real. Some practitioners have moved to manual warmup for Gmail specifically and automated for Outlook - a hybrid approach that hedges the risk.

Manual vs. Automated Warmup - What the Data Says

A study tracking 5,000+ domain warmups between 2024 and 2026 produced these head-to-head numbers:

Manual wins on quality. Automated wins on speed and scalability. The quality gap has narrowed - from 5.1 percentage points in 2024 to just 2.4 in 2026 as automated tools improved their engagement simulation.

The decision framework is simple:

• 1-2 domains: Manual warmup. The results are better and the time investment is manageable.
• 3+ domains: Automated. Nobody has 150-300 responsive contacts willing to reply daily across multiple inboxes for a month.

One pattern I keep seeing: experienced cold emailers abandoning automated tools entirely. One practitioner on Reddit put it bluntly - "too many red flags around using warmup services." His approach: start at 2-3 emails/day, ramp to 10-15/day per inbox, and rely on real engagement from actual prospects. Slower, but it works. If you've been burned by a warmup tool that tanked your reputation instead of building it, manual is the safe play.

My hot take: Most teams overthink warmup and underthink data quality. I've watched teams spend $200/month on warmup tools across 10 inboxes, then upload an unverified prospect list and blow up their sender reputation in a single afternoon. If you're running deals under $15K, you probably don't need a fancy warmup tool - manual warmup with clean data will outperform automated warmup with dirty data every single time.

Provider-Specific Rules for Warming Up Email Accounts

Gmail and Google Workspace

Gmail controls over 75% of the U.S. email market in 2026. Getting Gmail right is the whole game for most outbound teams.

Sending limits:

• Free Gmail: 100/day via SMTP, 500 via browser
• Google Workspace: 2,000/day
• Trial accounts: 500/day

New domain warmup on Google Workspace takes 8-12 weeks to reach full capacity. A new email address on an existing, active domain is faster - roughly one month.

The bad news: Gmail deliverability dropped to 12% for some senders in early 2026. Gmail now evaluates engagement quality - not just whether someone opened, but how long they read, whether they replied, and whether the conversation continued. Shallow engagement from warmup tools gets discounted.

Google's 2023 ban on automated warmup services still looms. Most tools work around it, but you're technically violating Google's terms. Factor that risk into your decision.

Microsoft 365 and Outlook

Outlook's story in 2026 is a reversal. After years of declining deliverability - inbox placement hit a dismal 26.77% in 2025 - Outlook improved in early 2026. Some practitioners reported better results from M365 accounts than Gmail for the first time.

The catch: M365 emails still struggle to land in Google Workspace inboxes. Gmail doesn't trust M365 IPs for new accounts, routing them to spam or blocking them outright.

The smart play in 2026 is running both providers. Diversify your sending infrastructure across Gmail and Outlook to hedge against whichever provider is having a bad month. Because in this environment, they take turns.

Email Warmup Before Sending: When to Start Real Campaigns

Don't start sending cold emails the moment your warmup volume hits your target. You need sustained positive signals first.

Green-light checklist:

• Bounce rate of 1% or less for 5+ consecutive days
• Unique open rate of 30-40%+
• Spam complaints near zero
• Inbox placement steady (check via mail-tester.com spot tests and Google Postmaster Tools)

Pause signals - stop immediately if you see:

• Spike in bounces or spam complaints
• Inbox placement dipping below previous baselines
• Microsoft throttling your sends

Here's a detail most guides miss: your warmup should hit a higher daily volume than your target campaign volume before you transition. If you plan to send 30 cold emails/day per inbox, your warmup should've been running at 40-50/day comfortably. This gives you headroom.

Once you start real campaigns, keep them tight. Instantly's 2026 benchmark data - drawn from billions of emails - shows 58% of all replies come from the first email. Steps 4+ barely produce anything. Keep campaigns to 3 steps max, under 80 words per email, with a single CTA. Follow-ups framed as replies outperform formal reminders by roughly 30%.

Why Bad Data Destroys Your Sender Reputation

This is where most warmup guides stop and most outbound programs fail.

You've spent 8 weeks building sender reputation. You've got green signals across the board. Then you upload a prospect list with 12% invalid emails and torch everything in a single afternoon. I've seen it happen to teams who did everything else right - and it's infuriating.

B2B email addresses decay at 2-3% per month. People change jobs, companies restructure, domains expire. The industry benchmark for B2B bounce rate is 2.0%. One campaign with a 10%+ bounce rate can undo weeks of warmup progress - inbox providers interpret high bounces as a signal that you're scraping or buying lists, and they respond by throttling or spam-foldering your future sends.

Any reputable verification tool works. The point is: never send to an unverified list. Your warmup investment is only as good as the data you feed into it. (If you need a process, start with a simple email verification list SOP.)

Warmup Tool Comparison and Pricing

The warmup tool market ranges from $5/month add-ons to $149/month enterprise products. Effectiveness varies wildly - a Snov.io test of eight tools on identical fresh Gmail accounts produced scores ranging from 29/100 to 94/100. The tool you pick matters.

The typical cost for a standalone warmup tool is $15-30/month per mailbox. If you're running 5 inboxes, budget $75-150/month for warmup alone.

A cautionary tale: Apollo killed its warmup feature in 2024 and replaced it with "Inbox Ramp Up" - which is just volume pacing with no engagement simulation or spam rescue. If your cold email platform says it includes "warmup," check whether it's actual warmup (sending to a network of real inboxes that engage) or just volume throttling. They aren't the same thing.

Skip InboxAlly and Folderly unless you're sending at marketing-level volumes (100K+/month). For most teams, TrulyInbox or MailReach hit the sweet spot of price and effectiveness. If you're already on Lemlist, Lemwarm is free with your subscription - no reason not to use it. And if you want one platform for everything - cold email sequencing, warmup, lead management - Instantly at $37/month is hard to beat, even if its warmup isn't the absolute best standalone option. (If you're evaluating platforms, this list of cold email outreach tools will save you hours.)

Beyond Warmup - Maintaining Deliverability Long-Term

Warmup isn't a one-time event. It's an ongoing discipline.

The teams hitting 10.7%+ reply rates (top 10% per Instantly's 2026 benchmarks) aren't just good at writing emails - they're obsessive about infrastructure maintenance. Here's what that looks like in practice:

Keep warmup running continuously alongside your campaigns. Allocate 20-30% of your daily send capacity to warmup traffic, even months after your initial ramp.

Re-verify your prospect list every 30 days. Email addresses decay at 2-3% per month - that's 25-35% annual churn. Build re-verification into your workflow, not as an afterthought.

Scale by adding warmed inboxes, not by spiking volume on existing ones. Need to double your outbound? Double your inboxes and warm each one individually. Some aggressive teams run 100 domains x 5 mailboxes = 500 sending addresses at 10 emails/day each. That's 5,000 cold emails daily without any single inbox exceeding safe limits.

Use heavy spintax to avoid pattern detection. Gmail's algorithms flag identical or near-identical messages sent at volume. Vary your opening lines, CTAs, and sign-offs across sends.

The average cold email reply rate is 3.43%. The top 25% hit 5.5%+ and the top 10% hit 10.7%+. The gap between average and excellent isn't copywriting talent - it's infrastructure discipline: clean data, warmed inboxes, authenticated domains, and tight 3-step sequences. (If you're building the rest of the system, start with a proven B2B cold email sequence.)

FAQ

Can I skip warmup if my domain is old?

No. A 10-year-old domain still needs warmup if it's never been used for outbound email. Inbox providers evaluate sending behavior and engagement patterns, not domain registration age. Dormant domains carry no positive signal history, so providers treat them almost like new senders.

Should I use Gmail or Outlook for cold email in 2026?

Run both. Gmail controls 75%+ of the U.S. email market but deliverability dropped sharply in early 2026, with some senders reporting 12% delivery rates. Outlook improved after years of decline. Many practitioners now send from both providers simultaneously - whichever one is struggling, the other picks up slack.

How long does it take to warm up an email address?

Brand-new domains need 8-12 weeks starting at 5-10 emails per day, increasing 10-20% weekly while bounces stay under 1% and opens above 30%. Existing domains with no outbound history need 3-6 weeks. Most practitioners cap at 30 cold emails per inbox per day even after warmup, adding more warmed inboxes for higher volume.

Do I need a warmup tool, or can I do it manually?

Manual warmup produces slightly better inbox placement (93.7% vs. 91.3%) and costs nothing beyond 30-60 minutes per day. Use manual for 1-2 domains. Automated tools like TrulyInbox or MailReach cost $15-30/month per mailbox and save significant time at 3+ domains. The quality gap narrowed to 2.4 percentage points in 2026.

What's the best free way to protect warmup with verified data?

Prospeo's free tier includes 75 verified emails per month with full 5-step verification, catch-all handling, and spam-trap removal - enough to validate your first campaign batches. Other free options include Hunter (25 searches/month) and NeverBounce's trial credits, though neither matches the 98% accuracy on a 7-day refresh cycle that Prospeo offers.