Are your cold emails landing in spam? For a brand-new domain, that is the default until you earn some trust. Here’s the part most guides skip. Since February 2024, Google’s Gmail expects anyone sending 5,000 or more messages a day to personal Gmail accounts to authenticate their mail and keep spam complaints under 0.3%, and Yahoo and Microsoft now enforce similar rules. Warmup is how you build that trust before you ever send a pitch.

In this guide, I’ll show you exactly how I warm a new email account the right way in 2026: the 3-to-5-week schedule I follow, the daily sending limits that keep you safe, the authentication providers now check for, and the tools that run the whole thing for you.

By slowly increasing your sending volume and frequency, and earning engagement like opens and replies, you build a sender reputation with internet service providers. Once they know and trust you as a legitimate sender, they let more of your emails reach the inbox.

Email warmup (also called IP warming) covers more than volume. It also depends on frequency, meaning how often you send, and on engagement, meaning how recipients interact with your emails.

It’s worth noting that sending domains, and the individual inboxes on them, sit at different stages of warmup. Where you stand depends on the age of the domain and its past sending activity.

How do you spot a spammer? You look at their behavior.

Spammers spam, so they never build a solid sender reputation. They blast out hundreds of emails at once and hope a few people open them. Internet and email providers watch for exactly this pattern, and their spam filters are built to catch it. When a sender gets flagged, their reputation takes a real hit.

The lesson is simple. Don’t behave like a spammer. Warm up gradually instead. Skip warmup and you can torch your sender reputation on day one and land straight in the spam folder.

The inbox providers tightened the rules, and that changed the stakes. Authentication and gradual warmup used to be nice-to-haves. Now they are the price of entry.

Since February 2024, Google’s Gmail has required senders of 5,000 or more messages a day to personal Gmail accounts to authenticate with SPF and DKIM, publish a DMARC policy of at least p=none, and keep their user-reported spam rate below 0.3%. Yahoo rolled out matching bulk-sender rules over the same period: SPF and DKIM, a DMARC policy, a one-click unsubscribe honored within two days, and that same 0.3% spam ceiling. Microsoft joined in too. From May 5, 2025, Outlook began routing mail from non-compliant domains that send 5,000 or more emails a day to Outlook.com, Hotmail.com, and Live.com straight to the Junk folder, with outright rejection planned as a later phase.

Those 5,000-a-day thresholds target high-volume senders, so a small team may sit under them today. The trust signals behind the rules apply to everyone. A new domain that suddenly sends hundreds of emails still looks suspicious, whatever your total volume. Warmup, done alongside proper authentication, is how you prove you are the real thing.

There are plenty of reasons to warm up, and they compound over time. A warmed inbox lands more often, so more recipients see and open your emails. Your sender reputation climbs, which validates you as a trustworthy sender with the providers. Your bounce and spam-flag rates stay low because you never spike your volume. Engagement rises, so you get more clicks and replies from prospects. You stay aligned with provider guidelines, which lowers the risk of being blacklisted or suspended. Your analytics get cleaner and more reliable to act on. And you build a foundation that keeps outreach performing for the long haul.

A warmup service sends and receives warmup emails on your behalf. It gradually raises the volume and frequency while replying to your messages, all on autopilot, so you don’t have to touch it.

Warming up an inbox by hand is tedious and slow. A service automates the whole thing, which frees you to focus on higher-value work like writing better outreach or closing more deals. In practice, it sends warmup emails on a schedule, opens them, replies from other inboxes in its network, and keeps that loop running for you. The better services also personalize the warmup content and send you deliverability alerts when something looks off.

A warmup schedule pushes your volume up steadily until you reach your target sending capacity, without hurting your reputation along the way. By ramping slowly, you earn trust from the providers and keep landing in your audience’s inbox.

The sweet spot for warming a new address is about one month, roughly 3 to 5 weeks.

With that ceiling in mind, keep the schedule simple. Send one email on day one, two on day two, three on day three, and add one more each day until you reach 20 warmup emails a day around day 20. That leaves room for about 20 outreach emails a day on that inbox.

Once you hit 20 warmup emails, keep warmup running and wait another week or so before you start outreach. My tip: during the initial phase, try not to send outreach at all. If you decide to, start with a low volume and ramp up slowly each week.

Need more outreach volume than one inbox allows? To send more, you use several warmed-up inboxes and spread the load with inbox rotation, so no single account gets hammered.

You can warm up without a service, but it’s a grind. Unlike a tool that handles everything, manual warmup puts the whole process on you. You have to follow a schedule, write and send the warmup emails yourself, keep replies healthy (aim for more than 50%), and never let the process lapse.

As you’ll see in the next section, warmup is never truly finished. You have to keep it running to hold onto strong engagement. Doing all of that by hand doesn’t scale, and it’s a slow way to stay out of the spam folder.

Most people think they can switch warmup off once the inbox is warm. That’s a rookie mistake. You should always have warmup running quietly in the background.

Why? Because cold outreach tends to earn lower engagement than everyday email, and that dip can drag down your deliverability. Keeping warmup on ensures a healthy stream of replies, which props up your sender reputation and, in turn, your open rates and conversions.

A healthy reply rate for outreach sits above 10%. Getting replies isn’t the whole story, though. You also want positive replies. Keep those above 1% and you’re in good shape, with 1% to 5% being excellent.

Authentication adds a layer of security to your emails, and providers reward that with better inbox placement. You set it up by adding specific DNS records to your domain.

The three protocols to configure are worth understanding. SPF tells inbox providers which servers are allowed to send mail from your domain. DKIM protects your emails from being tampered with in transit. DMARC decides what happens to messages that fail those checks. Together they make email a safer channel, and they distance you from the senders providers don’t trust.

These are the same records Gmail, Yahoo, and Outlook now expect, so get them in place before you start warming up. Click each protocol above for step-by-step setup instructions.

Once you understand the schedule and the rules, the practical question is who runs it for you. This is where lemlist comes in, and deliverability is built into the platform rather than bolted on.

It starts with lemlist’s deliverability setup. You can connect an existing domain in seconds or buy a fresh sending domain right inside lemlist, and authentication, meaning your SPF, DKIM, and DMARC records, is configured automatically. From there, lemlist caps your daily sends per inbox and pauses before you hit unsafe limits. It also lets you set sending windows by timezone and matches your sender to the recipient’s provider, so Gmail talks to Gmail and Outlook to Outlook.

Warmup itself runs on lemwarm, our built-in warm-up and deliverability booster that comes with every lemlist seat. lemwarm exchanges real emails across a network of more than 10,000 real accounts and generates human-like content for each message, so your inbox builds a reputation through genuine conversations rather than fake traffic.

When you scale past a single inbox, inbox delivery spreads your sends across multiple mailboxes with automatic inbox rotation, runs a pre-send Deliverability Boost that flags risky content or misconfigurations before you send, and verifies addresses to cut bounces. To see whether all of this is actually working, monitoring and alerts tests your inbox placement across Google and Microsoft, shows whether you land in primary, promotions, or spam, and sends real-time alerts the moment bounce or spam rates climb, with a per-mailbox technical audit to point you at the fix.

That’s why more than 20,000 sales teams run their outbound in lemlist. Warm up, launch personalized outreach sequences, and keep deliverability handled from one place.

lemwarm isn’t the only option, and I’ll be honest about that. Standalone warmup tools exist, and several of them work well for teams that only need a warmup layer on top of another sending tool. Pricing and features on these tools change often, so check each one at the source before you commit. That said, once you are also authenticating domains, rotating inboxes, and watching placement, an integrated setup is simply easier to run than stitching separate tools together.

You’ve warmed up your account. What now? Keep four things in mind. Leave warmup enabled even after you reach your target delivery rate. Increase your sending volume gradually rather than in jumps. Track your deliverability continuously. And watch your inbox placement across Gmail and Outlook so you catch problems before they cost you replies.

Tracking your deliverability comes down to watching the right numbers. Your delivery rate tells you how many emails reached the receiving server, while your deliverability rate tells you how many got past the filters and into the inbox.

One caution: tracking opens and clicks can now hurt you. Providers want to keep promotional mail away from users, and a tracking pixel signals a commercial email, so use open tracking sparingly.

Beyond that, keep an eye on your spam rate and spam-complaint rate, which show how often you’re marked as spam or reported by recipients. Watch your soft bounces, which reflect temporary issues like a full inbox, and your hard bounces, which point to permanent failures like an invalid address. Together these numbers tell you how healthy your sending really is.

Warmup isn’t complicated once you strip it back. Authenticate your domain with SPF, DKIM, and DMARC. Ramp your volume gradually over 3 to 5 weeks. Keep warmup running even after outreach starts. And watch your inbox placement so nothing slips.

Do that consistently and you give every campaign the best shot at the inbox. If you’d rather not manage the schedule, the authentication, and the monitoring by hand, lemlist runs all of it for you, with lemwarm included in every seat. Start a 14-day free trial and let deliverability take care of itself while you focus on booking meetings.

Warming a new address usually takes about 3 to 5 weeks. You add one warmup email per day until you reach roughly 20 a day, then keep it running. Warmup never fully stops, though. To protect your reputation, keep it on even after you start sending outreach.

You can warm up manually by following a schedule and sending, opening, and replying to emails yourself, but it doesn’t scale and it’s easy to let slip. For anything beyond one or two inboxes, a warmup tool automates the whole loop and keeps it consistent, which is why most outreach teams use one.

The process is the same for both: authenticate the domain, ramp your volume slowly, keep engagement high, and let warmup keep running. A helpful edge is provider matching, where your sender is paired to the recipient’s provider so Gmail sends to Gmail and Outlook to Outlook. lemlist handles that matching automatically.

Focus on where your emails actually land. Inbox placement across Google and Microsoft tells you whether you’re hitting primary, promotions, or spam. Your sender reputation and spam rate show how providers see you. Keep your reply rate above 10% and your spam rate low, and you’re on track.

The big ones are skipping authentication before you send, ramping volume too fast, sending outreach during the early warmup phase, and turning warmup off the moment an inbox looks warm. Go slow, keep warmup running, and watch where you land.

For a brand-new address, start with one email on day one, then add one more each day until you reach 15 to 20 warmup emails a day. Keep your total daily sends modest, around 40 per inbox, so you never look like a bulk sender before you’ve earned the reputation.