How to Warm Up Email Domain (2025)

Starting cold email campaigns from a fresh domain? Pump the brakes.

Email providers like Gmail and Outlook immediately flag new senders blasting out messages with zero history. If you skip the warm-up process, your carefully crafted emails could land straight in spam (or get blocked entirely) before anyone ever sees them. Research from Outbound System shows that skipping this step is basically a guaranteed ticket to the spam folder.

Warming up an email domain means gradually building the domain's sender reputation so that inboxes trust your messages. In this guide, we'll explain what domain warm-up is, why it's critical in 2025, and step-by-step how to do it right with actionable tips to maximize deliverability.

Whether you're launching cold outreach on a brand-new domain or reviving a dormant one, this is the playbook to ensure your emails land in the inbox.

Why Email Domain Warm-Up Matters

Whenever you start sending emails from a new or little-used domain, email service providers (ESPs) immediately put you under the microscope. Research shows that to these providers, a new domain sending bulk emails is suspicious by default. It could be a spammer or botnet.

Domain warm-up is how you prove the opposite: that you're a legitimate sender who sends wanted, high-quality emails. By starting with low volume and ramping up gradually, you accumulate positive sending history and earn the trust of mailbox providers over time. Industry data shows this approach works because providers see consistent, good behavior rather than sudden suspicious spikes.

If you don't warm up a new domain, the consequences are almost guaranteed: major providers will throttle your messages, route them to spam, or block them outright. All your cold email campaign effort can go to waste.

On the other hand, a proper warm-up leads to a positive sender reputation. Providers see good engagement, low bounces and complaints, and consistent patterns. That reputation is what gets your future emails delivered to inboxes instead of junk folders. Before you start sending large volumes, you need this foundation in place.

The core principle: Warming up your email domain is all about building trust. You're essentially saying to Gmail, Outlook, Yahoo, etc., "Hi, I'm a responsible sender. People engage with my emails, and I don't send spam."

Do it right, and after a few weeks those providers will lift the sending limits and spam suspicions, allowing your campaigns to scale. Do it wrong (or not at all), and your outreach may never reach its audience.

What Is Email Domain Warm-Up?

Email domain warm-up is the process of gradually increasing the email sending volume from a new or "cold" domain over a period of time, while maintaining excellent engagement and low spam signals, in order to build up the domain's reputation with email providers.

According to industry standards, think of it like exercising a new muscle: you start light and slowly increase the load.

In practice, this means sending a small number of emails on day one, a bit more the next day, and so on. All to recipients who are likely to open and interact with those emails. As the positive interactions accumulate without any red flags (like bounces or spam complaints), the domain gains credibility.

During the warm-up phase, consistency and quality are key. ISPs track metrics such as:

Sending Volume Patterns

Are you sending a consistent, modest volume that grows slowly (good), or did you jump from 0 to 5,000 emails overnight (bad)?

A new sender should avoid any sudden spikes. Data from Outbound System shows consistency matters enormously. Gradual, steady growth is viewed favorably.

For example, a domain that sends 20 emails one day and 40 the next is fine, but going from 20 to 2,000 in one leap will trigger alarms.

How to Keep Bounce Rates Low

Are your emails reaching valid addresses?

Critical deliverability rule: A high bounce rate signals poor data quality and will quickly damage your reputation. Keep hard bounces under 2% at all times.

Research indicates that invalid addresses tarnish your reputation quickly, so use clean, verified lists from the start. Outbound System's 9-step waterfall enrichment ensures bounce rates stay minimal.

Avoiding Spam Complaints

Are recipients marking you as spam?

Even a 0.3% complaint rate is too high. Industry analysis shows every time a recipient hits "Report Spam," it's one of the deadliest factors for sender reputation.

In the warm-up stage you ideally want zero spam complaints. This is why you send only to friendly or engaged contacts early on.

Maximizing Email Engagement

Are people interacting positively (opens, replies, clicks) with your emails?

Lots of replies and minimal deletions or ignores tell providers that your content is wanted. Mailbox providers increasingly factor in engagement as a measure of sender quality.

Getting recipients to actually reply during warm-up can hugely boost your sender reputation.

By the end of a proper warm-up (often around 4 weeks of gradually increasing sending), your domain should have a "trustworthy" reputation in the eyes of Gmail, Outlook, and others. New domains typically need at least 4 to 6 weeks of consistent, high-quality sending to build a solid sender reputation.

After this warm-up period, you'll be able to send at scale with far less risk of being throttled or junked, as long as you continue following best practices.

Important note: It's not only domains that have reputation. IP addresses and individual email addresses do too. Most modern filters primarily look at domain reputation (especially if you're on shared IPs), but if you use a dedicated IP, that IP must be warmed up as well.

In any case, ensure you set up proper email authentication (SPF, DKIM, and DMARC) on your domain before sending any warm-up emails. As of 2025, Gmail and Microsoft require authentication for bulk senders, and Microsoft will even expect a DMARC policy if you send more than 5,000 emails per day.

These DNS records prove your emails are legit and not forged, which is a baseline for building trust.

Now that we know why warm-up is critical, here's how to do it step by step.

How to Warm Up a New Email Domain (Step-by-Step)

Warming up an email domain is a multi-week process. Below is a proven step-by-step plan that many cold email experts follow to ramp up safely.

We'll break it down by phases (weeks), since warm-up is typically measured in weeks of gradual scaling.

Week 1: Start Small with High-Quality Contacts

① Send only 10 to 50 emails per day, max, in the first week

Research shows it's better to err on the lower side (e.g., 10 to 20 per day for a brand new domain) and make sure these initial emails are to your most engaged, friendly contacts. This week is all about building initial trust.

Ideally, this means people likely to open, read, and reply. Think colleagues, friends, or opt-in contacts who already know you. These positive engagements (opens, clicks, replies) are gold for your sender reputation early on.

② Personalize the emails and avoid anything spammy

During warm-up, your goal isn't to sell or blast a generic template. It's to look like a real person sending a normal one-to-one email. Research shows reputation builds early on through natural interactions.

Keep your messages short, plain-text, and personalized (no big images or marketing buzzwords).

Don't use "spammy" language (e.g., all-caps or phrases like "Act now, 100% FREE!!!") that could trigger filters. Industry best practices recommend avoiding these obvious spam signals.

You want these emails to land in the primary inbox and get a response, so write them accordingly. For example, you might send a simple check-in email:

"Hi [Name], just making sure this email works. I'll follow up soon. Hope you're well!"

Something that encourages a quick reply. Every genuine reply or click is a positive signal to the ESPs that your emails are wanted.

③ Ensure zero bounces and complaints

In week 1, be extremely careful with your recipient list. Do not send to any unverified or stale addresses yet. You want to start your warm-up with contacts who will engage positively.

If even a handful of those initial 50 emails bounce or lead to "Report Spam" clicks, you've hurt your domain on day one.

So use only known good emails (or better yet, manually double-check them). The same goes for unsubscribes or spam flags. They should be zero in this phase. Clean list building is essential from day one.

By the end of week 1, you want your domain to have a record of around 50 to 200 total emails sent, with near-100% delivery and maybe even a few real replies.

Weeks 2-3: How to Gradually Increase Email Volume

④ Double your sending volume each week if metrics stay healthy

After week 1, if you had no major issues (very few bounces, no spam complaints), you can start gently increasing your daily send count. A common rule of thumb is to roughly 2× your volume per week. Experts recommend slowly increasing your daily volume.

For example:

• If you sent around 20 per day in Week 1, go to around 40 per day in Week 2

• Then around 80 per day in Week 3

Maintain a consistent sending schedule (e.g., emails spread out at a regular pace each day, not all at once) so that providers see a stable pattern. This helps ESPs recognize your pattern. Avoid erratic jumps. Steadiness is the name of the game.

⑤ Broaden your recipient list slightly, but still prioritize quality

In weeks 2 to 3, you can expand beyond just your ultra-engaged contacts to some "warm" recipients. Maybe folks who know of your business or semi-engaged users.

However, do NOT yet hit your coldest prospects or large purchased lists. You're still in reputation-building mode.

Every email you send in warm-up should ideally get opened or at least not bounced. As you add a bit more volume, keep monitoring your bounce rate and spam rate like a hawk.

If you see any warning signs (e.g., bounce rate creeping above around 2% or a spam complaint or two comes in), pause and address it before continuing to increase volume. Begin with small sends to ensure engagement stays high and bounce rates near zero.

It's better to extend the warm-up longer than to push too fast and get blocked.

⑥ Keep emails human and encourage engagement

This advice from week 1 continues here: as you send more emails, make sure you're still getting positive engagement. For instance, you might ask a question in your email that invites a reply (even something simple like "Does that sound reasonable to you?").

Replies are one of the strongest positive signals for deliverability.

Also ensure your content is non-spammy and relevant to the recipient, so they don't ignore or delete it. Mailbox providers track if users read or quickly delete your emails. Behavioral signals matter significantly.

You want to avoid patterns of mass-deletion which indicate low interest. By the end of Week 3, you might be sending on the order of a few hundred emails per day, still largely to safe audiences, and your domain should be gaining a solid footing if engagement remains good.

Week 4+: How to Scale to Full Sending Volume

⑦ By Week 4, begin reaching your target volume and include "colder" contacts

If everything has gone well in the first 3 weeks, you can start to open the throttle in week 4 and beyond. This is when you reach full volume. This means approaching the daily volume you eventually plan for regular campaigns.

For example, if your goal is to send around 500 emails per day, you might ramp up to that level in week 4. Some experts suggest that by week 4 you can start adding in the colder prospects or larger new lists. But only if they are cleaned and verified.

By now, if everything's looking good, you can start scaling your outreach.

Don't suddenly mail 10,000 completely cold addresses in week 4. Rather, fold in new segments gradually and keep an eye on results. Continuously monitor your domain's health as you reach full volume: use tools like Google Postmaster Tools to see your sender reputation with those providers.

These monitoring tools help track engagement, sender score, and deliverability.

If you notice any reputation dip or spam placement, hold off on further scaling and investigate.

⑧ Maintain consistency and don't stop abruptly

After about a month of ramp-up, your domain should be "warmed" and able to handle your normal sending volumes. But remember, sender reputation is ongoing. You need to keep sending consistently to maintain it. Consistency helps build a stable reputation.

Don't warm up for a month and then suddenly go dark for weeks, only to blast a huge campaign later. That inconsistency could raise flags all over again. Maintain consistent sending patterns even after warm-up completes.

Try to maintain a baseline of activity on the domain (even if small) so that ISPs see continuous, normal usage. And of course, keep following email best practices (list hygiene, relevant content, etc.) beyond the warm-up phase to preserve the hard-earned reputation.

To summarize the timeline:

Start around 10 to 30 emails per day in week 1, double weekly (approx. 50, then 100, then 200, then 400, etc.), and reach your desired sending volume after about 4 to 6 weeks. A rule of thumb is to gradually double each week.

This slow-and-steady approach builds credibility gradually instead of alarming ISPs with sudden bursts. Building a strong sender reputation takes time, but once established, you can send at full volume.

Throughout the process, monitor key metrics: keep hard bounces below 2%, spam complaints below 0.1%, and aim for solid open and reply rates. If you stick to the plan, by the time you hit full volume you'll have a healthy sender reputation that gives your cold email campaigns a fighting chance of inboxing.

Best Practices to Boost Deliverability During Warm-Up

Following the step-by-step volume plan is essential, but it's not the only factor in a successful warm-up. How you send and what you do in parallel also matter. Here are crucial best practices and tips to make your domain warm-up as smooth and effective as possible:

How to Set Up Authentication & Infrastructure First

As noted earlier, always implement SPF and DKIM records on your sending domain, and publish a DMARC record, before you start sending warm-up emails. This is non-negotiable for modern email providers. This authenticates your messages and prevents them from getting flagged as spoofed or untrustworthy.

Also, send your warm-up emails from a consistent domain and sender name. If possible, use a dedicated subdomain for cold outreach (e.g., outreach.yourcompany.com) separate from your main corporate domain.

Many teams do this to isolate reputation. So if something goes wrong, the main brand domain isn't affected. Industry best practices suggest using separate infrastructure for cold outreach.

Warming up a subdomain works the same way as a root domain, and it can be a smart strategy to protect your primary domain's email reputation. Some companies use separate subdomains for different types of outreach to maintain clean reputation segmentation.

Start with One Mailbox Per Domain

If you plan to have multiple email accounts (mailboxes) sending from the same domain, don't start warming them all at once. It's recommended to warm up with one mailbox first, get the domain to a good baseline reputation, and then gradually add additional mailboxes to the sending rotation.

Quick heads-up: warm up one inbox first, then add more accounts into the mix.

Adding too many new senders on the domain simultaneously can multiply the volume and risk beyond what the domain's history supports. Once the first address is warm, the domain is less likely to be penalized when a second or third address starts sending (still ramp those up slowly too).

How to Keep Your Email Lists Clean

No bounced emails, period.

Use email verification tools to scrub your list before every stage of warm-up. As a rule, never upload a big unverified list to your sequence, especially during warm-up. Even much later, list hygiene remains vital.

A single campaign with a bounce rate above 5% can seriously hurt your reputation almost overnight. How quickly can a bad email list damage your reputation? Very quickly.

During warm-up, you should target a 0% bounce rate if possible (since you're emailing known contacts). This also means avoiding any purchased or scraped lists at this stage. Those are often full of invalid addresses and even spam traps.

One spam trap hit can blacklist your domain.

Build your sending list carefully and remove any address that doesn't positively engage as you go. Learn more about building clean B2B lead lists.

Avoid Spam Trigger Words and Content

Email content affects deliverability more than many realize. While warming up, stick to plain, genuine language. Absolutely avoid known spam trigger words and formatting (e.g., "FREE MONEY!!!", excessive exclamation marks, ALL CAPS, or misleading subject lines). Industry guidelines recommend clean, simple content.

Also ensure your emails are text-based or lightly formatted. Heavy HTML, attachments, or large images can raise suspicion for a new sender. Focus on conversational tone.

Not only does this help you stay out of spam, it also makes it more likely recipients will respond, which helps your cause. Check out our guide on writing effective sales emails.

In addition, include an easy way to opt-out if you're doing any kind of bulk outreach beyond one-to-one (a simple line like "P.S. let me know if you prefer not to get emails from me" or a formal unsubscribe link). Google and Microsoft now expect even cold emails to provide an opt-out method.

While a handful of initial warm-up emails to friends might not need this, by the time you reach larger volumes it's wise to include, as it reduces the chance someone hits the spam button.

How to Engage with Replies and Interactions

Try to generate positive engagement on the emails you send. If a contact replies, great. Make sure to reply back (carry a short conversation if appropriate). These back-and-forth replies are huge trust signals.

Some teams even coordinate internally or with friendly partners to reply to each other's warm-up emails on different providers, to show cross-domain engagement.

Additionally, encourage recipients to perform small actions that help your reputation: for example, asking them to mark your email as important or add you to their contacts can boost your deliverability with that provider over time. Even a few recipients doing this during warm-up can help establish your domain as welcomed.

How to Monitor Your Sender Reputation

Don't fly blind during a warm-up. There are free tools to check how ISPs view your domain. Google Postmaster Tools is a must. It will show your domain's reputation in Gmail (once you've sent enough volume and verified the domain). Yes, you can check your sender reputation to see how providers view your sending reputation.

It will classify your reputation as High, Medium, Low, or Bad. Aim to keep it "High" once you ramp up. Microsoft's SNDS is similar for Outlook and Hotmail accounts.

Additionally, you can use reputation monitoring services to see if your domain or IP has any negative marks. Building a strong sender reputation requires monitoring.

During warm-up, check these at least weekly. If you see a sudden drop in reputation or a blacklist listing, act immediately. Pause sends and fix the root issue (whether it's content, list, or technical).

Early detection can save you from a total shutdown of deliverability. Learn how to reduce email bounce rates to maintain reputation.

Know Your Email Provider's Limits

Different email sending platforms (ESP) have different sending limits, especially for new accounts. Here's a quick reference:

If you're using an email service or CRM, they may have their own ramp-up policies too. Make sure you're aware of these limits and stay well below them during warm-up. Also, sending too close to the cap consistently can raise flags, so build in a buffer.

Pro tip: avoid doing your cold outreach from free email accounts entirely. Not only are their limits low, but free webmail domains (especially Yahoo, AOL, etc.) are more closely associated with spammers and can hurt credibility. Look into using professional business domains with proper infrastructure setup.

Should You Use Warm-Up Automation Tools?

Manually warming up a domain (finding engaged contacts, sending emails every day, tracking replies, etc.) can be tedious and time-consuming. The good news is there are tools that automate the warm-up process by having your email account send messages to and from other real inboxes in a network.

For example, some cold email platforms include built-in warm-up networks. These tools will automatically send emails from your account to other participants and even auto-generate positive engagements (like replies, marking messages as "not spam", etc.) to quickly boost your reputation. Professional warm-up services can handle this process for you if manual warm-up sounds tedious.

Essentially, they create a sandbox of emails that make you look good to email providers. A quality warm-up tool will also monitor your DNS settings (SPF/DKIM) and deliverability metrics as it works. Features include gradual volume ramp and DNS configuration checks.

If manual warm-up sounds like a chore, it's because it is. So leveraging a tool or service can save a lot of effort. Just ensure any tool you use is reputable (watch out for any that send obviously fake or spammy messages on your behalf, as some lesser tools might do more harm than good).

The best services use AI or vetted content to make the interactions appear natural. Once you connect your inbox, quality systems generate realistic conversations that sound like actual interactions.

At Outbound System, we automatically handle domain warm-up for all our clients. Our infrastructure uses 350 to 700 Microsoft U.S. IP inboxes (depending on your plan) that are already warmed and maintained. This means when you start a campaign with us, you're leveraging pre-warmed infrastructure with established sender reputation.

We also handle the 9-step waterfall enrichment to keep bounce rates near zero and use AI personalization to drive genuine engagement. Basically, we take care of the entire warm-up and deliverability process so you can focus on closing deals, not managing email infrastructure.

Maintain Long-Term Sending Practices

Warm-up doesn't end with hitting your volume goal. Carry forward the same principles into your ongoing campaigns. Maintain a consistent sending frequency (don't go from sending daily to vanishing for a month). Maintain consistent sending patterns to keep your reputation stable.

Continue to verify new lists before adding them. Monitor every campaign's bounce and complaint rates. If something goes high, fix it immediately.

Also, as you scale, consider spreading your sending across multiple domains or IPs if volume is very high. This is a tactic known as "snowshoeing" (though do it ethically, not to hide spam, but to keep each domain's volume moderate). Many large-scale senders operate with several domains to compartmentalize reputation.

The bottom line: think of sender reputation as an ongoing asset to manage, not a one-time project. Warming up is just the first phase of that stewardship. Explore scalable B2B sales outreach workflows for long-term success.

How Outbound System Handles Email Warm-Up

If all of this sounds like a lot of work... well, it is. Managing sender reputation at scale can be complex and time-consuming. That's one reason many companies turn to specialized partners for help.

At Outbound System, we've built our entire infrastructure around solving deliverability challenges. Here's how we handle email warm-up and domain reputation for our clients:

Private Microsoft Infrastructure

We use hundreds of private Microsoft Azure U.S. IP inboxes (350 to 700 per client depending on plan) that are already warmed up and maintained. This means when you start with us, you're not warming up from scratch. You're leveraging an established infrastructure with proven sender reputation.

Learn more about Microsoft Azure servers and cold email deliverability.

Because we distribute sends across many inboxes, each individual inbox stays under spam detection thresholds while maintaining your overall volume. This mimics natural human sending patterns rather than high-volume automated patterns that trigger filtering.

9-Step Waterfall Enrichment

One of the biggest reputation killers during warm-up (and beyond) is bounced emails. That's why we run every single email address through our 9-step waterfall enrichment and triple verification process before it ever enters a sequence.

This includes:

• Syntax validation checks

• SMTP ping verification

• Historic bounce data analysis

• Engagement signal evaluation

The goal is to minimize hard bounces (which damage sender reputation) and maximize reply probability by ensuring contact accuracy before we initiate outreach. We verify every email address before sending.

AI Personalization with Human Copy

Cold emails need to feel personal and relevant to generate positive engagement. We combine human-written copy with AI personalization to create prospect-specific messages.

Our copywriters establish the core value proposition and structure, while AI systems generate personalized lines based on prospect data, company information, and relevant triggers. This approach drives 2.8× higher response rates compared to generic templates, which helps maintain positive engagement signals during warm-up and beyond.

Check out our cold email templates for inspiration.

Continuous Monitoring and Optimization

We monitor deliverability metrics in real-time through Google Postmaster Tools, Microsoft SNDS, and our internal analytics. If we see any reputation dip or spam placement, we adjust immediately. This proactive monitoring ensures your sender reputation stays healthy as we scale your campaigns.

Plus, with our month-to-month contracts and transparent pricing starting at $499/month, you're not locked into long-term commitments while we prove the value of our infrastructure. Learn more about why Outbound System is the best cold email agency.

The Bottom Line

Whether you DIY or get help, never ignore domain warm-up. It's the foundation of every successful cold email program. In 2025 and beyond, you simply won't survive the spam filters without doing this right.

If you want to skip the manual warm-up process and start with established infrastructure, book a free 15-minute consultation with our team. We'll show you how our warm-up process works and how we can get your cold email campaigns delivering to inboxes in as little as 14 days.

Common Questions About Email Domain Warm-Up

How long does it take to warm up a new email domain?

Typically about 4 to 6 weeks of steadily increasing sending is recommended to establish a solid reputation. New domains typically need at least 4 to 6 weeks of consistent sending to build trust with providers.

At minimum, you should give it a full month before sending at max volume. Rushing it faster is risky. Some senders do 2 to 3 weeks in a hurry, but they're playing with fire unless volumes remain low. It's better to be patient and ramp up gradually over several weeks.

Remember, the warm-up period is an investment in your deliverability. A bit of delay upfront can mean far better inbox placement when your big campaigns roll out.

Do I need to warm up an old domain I've never used for email?

Yes. If a domain has no sending history (or hasn't been used in a long time), it's effectively "new" to ISPs in terms of reputation. Even if the domain itself is years old, mailbox providers won't have any data on its sending behavior.

You should treat it like a new domain and perform a warm-up if you plan to send bulk emails. The age of the domain alone doesn't confer email credibility. Only sending history does.

One advantage of older domains is they might be less likely to be on any automatic newbie blocklists, but you still must build a positive reputation from scratch by warming up with good practices.

What about warming up a new IP address?

If you use a dedicated IP for sending (for example, via an SMTP service or your own mail server), you also need to warm up that IP by gradually increasing volume. In fact, many concepts are the same:

• Start with small sends to high-quality contacts

• Double volume slowly

• Monitor bounces and complaints

Often, you'll be warming up the domain and IP simultaneously (if both are new). Many ESPs handle IP warm-up for you via automatic throughput limits. But if you manage it yourself, apply a similar 4 to 6 week ramp timeline.

Keep in mind that both domain and IP reputation matter. Note: It is important to warm up both for emails to be delivered to your recipients. If either one has issues, it can hurt deliverability.

For most people using cloud email services, IP reputation is managed by the provider's pool, so domain warm-up is the main focus. But if you run on a dedicated IP, don't neglect warming it up too.

Can I send other types of emails during warm-up (newsletters, etc.)?

It's safest to keep the warm-up traffic "clean" and low-volume. If you have a scheduled newsletter or other campaign, ideally send it from a different established domain or IP until your new domain is warm.

You don't want to mix potentially unengaged audiences into your warm-up phase. That said, if the other emails are very low volume and to highly engaged subscribers, they might actually help your warm-up. Just avoid any big sends or anything that could generate complaints.

Some companies will initially use a new domain to send a trickle of internal emails or transactional emails (password resets, etc.) as part of warm-up, since those tend to have good engagement. The key is: during warm-up, every email you send should help your reputation, not hurt it. If in doubt, don't do it on that domain yet.

What if my warm-up is not going well (low open rates or spam block)?

If you encounter deliverability issues in warm-up, pause and diagnose immediately:

• Check your authentication (mistakes with SPF or DKIM can tank you, so fix those first)

• Look at your content for any spam triggers and simplify it

• Review your sending list: were there unexpected bounces or cold contacts sneaking in? Remove anything suspect

• Use deliverability testing tools to send a test from your domain and see if you're landing in Spam

If a particular provider (say, Gmail) is junking you early, you might slow down the ramp-up and send even fewer emails to Gmail addresses for a while, focusing on improving engagement with those that do go through.

Also, consider enrolling in feedback loops (FBL) for ISPs that offer them, so you get notified of spam complaints (for example, Outlook's SNDS and Smart Network Data Services can give insight if Outlook is junking you).

It's possible to recover during warm-up, but it might prolong the timeline. In worst cases, if a domain gets seriously flagged during warm-up (e.g., ends up on a major blacklist due to a spam trap hit), it might be easier to pivot to a new domain rather than spend months rehabilitating a brand new domain that started off on the wrong foot.

Learn from what went wrong (whether it was list quality, content, volume), fix it, and try again with a fresh domain if needed. But for minor blips, just course-correct and continue. One or two hiccups early on aren't fatal if you address them and resume sending good signals.

Once my domain is warmed up, how many emails can I send daily?

This depends on your infrastructure and the limits of your email service provider. A properly warmed domain can technically send thousands per day, but you must stay within your platform's allowed sending limits. Typical limits are shown in the table above.

If you need to send more than what one account allows, you might use multiple email accounts on the domain (each warmed up) or multiple domains in parallel.

Outbound System's infrastructure, for instance, uses hundreds of distributed inboxes to send millions of emails at scale while keeping each inbox under a low limit. We use 350 to 700 inboxes to distribute volume and maintain reputation.

The safe number also depends on your content and audience. If you send 5,000 emails per day and they all get solid engagement, you could possibly increase, but if engagement dips, you might need to dial back.

Never jump from say 500 per day to 5,000 per day overnight, even post-warm-up. Increase in increments and watch metrics. Also note that some providers have hourly limits as well, so large daily volume must be spread throughout the day.

Can I speed up the warm-up at all?

There's no magic shortcut to building trust. By design, it takes time. However, using automated warm-up tools can accelerate the feedback loop.

These tools might engage in hundreds of micro-interactions (opens and replies) on your behalf that would be impractical manually, thus signaling positive engagement faster. They can sometimes condense the warm-up window a bit (for example, achieving in 2 to 3 weeks what might take 4 to 5 weeks organically) because they ensure every email gets a reply or a "not spam" mark behind the scenes.

Professional warm-up automation tools work across major providers like Gmail, Outlook, and others.

Still, you can't go from zero to full blast in a few days safely. The providers themselves need to see a progression. So while you might use a warm-up service to optimize and maybe moderately shorten the warm period, don't attempt to completely bypass it.

Also, keep in mind that if you do rush and get burned (spam-blocked), it's counterproductive. You'll end up spending far more time fixing your reputation than the time you would have spent warming up correctly.

Should I warm up new domains continuously, even if I don't need them yet?

Some advanced senders will pre-warm additional domains as a proactive measure. For instance, if you anticipate scaling your outreach in the future, you might warm up another domain (or subdomain) in parallel so it's ready to go when you need to increase volume.

This isn't necessary for everyone, but it's a strategy to consider if you have the resources. By warming up a backup domain now, you have a fallback if your primary domain runs into deliverability issues or if you simply need to send more.

Just remember that any domain you warm up requires ongoing sending to maintain. A warmed domain that you then let sit idle for 6 months will need a mini warm-up again. So, if you do pre-warm domains, keep them active at a low level.

Many outreach agencies do maintain multiple domains and rotate sending among them to keep each one's volume moderate (this is related to the "snowshoe" approach for deliverability). It can add complexity, but it spreads risk.

Ready to Start Warming Up Your Email Domain?

Warming up an email domain is absolutely essential in today's email landscape. Yes, it requires patience and discipline, but the payoff is huge: higher inbox placement, better response rates, and campaigns that actually reach potential customers.

By following the guidance above (gradual volume increases, strict list hygiene, quality content, and constant monitoring), you'll significantly increase your chances of winning the trust of Gmail, Outlook, and all the other gatekeepers standing between you and your prospects' inboxes.

And if all of this sounds like a lot of work... well, it is. Managing sender reputation at scale can be complex and time-consuming. That's one reason many companies turn to specialized partners for help.

At Outbound System, we automatically handle domain warm-up and deliverability optimization for our clients, using a dedicated infrastructure of warmed-up addresses to ensure your cold emails hit inboxes ready to engage. We've sent 52M+ cold emails with 98% inbox placement and 6 to 7% response rates by handling all the technical complexity for you.

See how we compare to other cold email agencies.

Book your free 15-minute consultation to learn how we can help you skip the manual warm-up process and start sending at scale with established infrastructure. You can also explore our case studies to see real results we've delivered for clients across industries.

Now, take it slow, build that sender reputation, and happy emailing. Your future self (and your email recipients) will thank you.