Complete Guide to Email Warmup for Sales

How many emails should you be warming up and using in my your email outreach campaigns? The answer may surprise you…

What is Email Warmup?

Email warmup refers to the process of establishing a positive sending reputation for a new email sender or an email with damaged reputation. To warm up your email, you gradually send an increasing volume of emails over a period of 3-4 weeks while closely monitoring deliverability and engagement metrics. This gradual increase helps prevent spikes in sending activity that could trigger spam filters or ban algorithms from your ESP.

Boxward takes that a step further by automatically sending emails on your behalf to our network of users who agree to receive them, and automatically engaging with the emails we send in a positive way – marking them read, marking them important, replying to them, etc. This positive engagement with your emails trains ESPs to treat your emails as important.

The purpose of email warmup is to build trust with email service providers (ESPs) and email recipients, reducing the chances of your emails being marked as spam or ending up in the recipients’ junk folders.

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Why Should You Listen to Me?

When I started with cold emailing, I had no idea what I was doing.

It was definitely a learning experience to figure things out.

The first outreach I did was definitely bad. And I didn’t know much at all about email warmup. So it shouldn’t be a surprise that I had terrible open and reply rates.

We’ve now been sending cold emails for many years.

And, we also make tools that help others to send cold emails.

The question about how many emails to warm up and use in cold outreach is one we’ve gotten frequently. So, today we’re going to dive into it.

Spoiler: The short answer is “More than one”

Why is Email Warmup Important?

Email warmup helps ensure your emails reach your contacts’ inboxes.

Take this scenario for example:

You have a list of contacts’ email addresses.

So you email them.

But, these are all strangers who you’ve never emailed before.

It could be 100 contacts. It could be 1,000.

But, because these contacts are people who you’ve never emailed before, it’s generally going to be less likely that they reply to you compared with a person who knows you and you email regularly.

And email service providers – Google, Outlook, Zoho, Yahoo!, etc. – they’re tracking your emailing. They know all the people you’re emailing in their networks. They know the open and reply rates you’re seeing. And cold emails generally have a much lower reply rate than emails between colleagues who know each other. And, they also know if you are sending emails that look similar to each other (e.g. using an email template) to inboxes.

Google, Outlook, Zoho, and all the other email service providers are constantly working to ensure that irrelevant spam emails are not reaching people’s inboxes. To do this, they rely on their monitoring of emails, bounces, published blacklists, and email authentication.

To best ensure your emails avoid the spam folder and reach your contacts’ inboxes, that’s where email warmup comes in.

Email warmup is a process where your email address sends emails to other inboxes that are controlled by a particular email warmup network (for example, Boxward is an email warmup provider). You automatically email other inboxes in the network, those inboxes reply to your emails, and if your emails land in their spam folders, your emails get moved to their main inboxes. Email warmup is meant to “train” Gmail and other email providers to ensure that your emails land in the main inbox and not junk folders.

Email warmup should not only be done when you first set up a new email address that you’re going to be using for cold email. It should be used continuously. This is because if you stop email warmup and start sending a lot of cold emails, you may see your deliverability drop. Keeping your email warming up ensures that you are sending emails that are getting replies, marked “not junk”, and it helps ensure that email providers keep you landing in your contacts’ main inboxes.

Without email warmup, you will quickly see that your cold emails will be landing in your contacts’ junk folders, and your open rates / reply rates will drop drastically.


Why Warm Up Multiple Emails?

When doing cold emailing, it’s important to use multiple email addresses. And, related to this, it’s important to be warming up these multiple email addresses constantly.


A few reasons.

Being Able to Send More Emails

There are only a certain amount of cold emails that you can send safely each day per mailbox.

Each email service provider has daily email sending limits.

But, even with these daily limits, you can run into danger if you even get close to them.

For example, while Gmail may say that you can send up to 500 emails per day – if you were to try sending 500 cold emails per day with Gmail, you would most certainly get your account suspended by Gmail.

Gmail, and all the other email service providers, are quick to suspend accounts that have suspicious sending patterns. And most people aren’t sending anywhere near 500 emails per day. Especially not 500 emails per day that look very similar to each other, or to 500 contacts that you’ve never emailed before.

And, if you were to try to send 100 or 200 emails per day with Gmail, you would also likely see your deliverability drop along with your open and reply rates.

With cold email, the general rule of thumb is that you can safely send 30-50 emails per day per email address without being in danger of seeing deliverability drop or getting your email address suspended by your service provider.

(“But what about using an email sender like Mailchimp?” is a common question. Don’t do it. Not only does Mailchimp prohibit cold emailing, their platform is not at all meant for cold emails and your account will be quick to get suspended)

So, if you can send, at most, 50 emails per day, and you’re only sending emails on weekdays (don’t send cold emails on weekends), and there’s an average of 21 weekdays per month, that’s 1,050 emails per month. If it’s 30 emails per day, that’s 630 emails per month.

For sales lead generation cold emailing, that’s not a lot of emails.

Having multiple email addresses warmed up means you can send 2x or more cold emails each month.

One Email Address is a Bottleneck

Related to the issue of volume, if you have only one email address warmed up for cold emailing, that one email address becomes your bottleneck.

You can only send 1,050 emails per month, and no more.

If you have a list of 5,000 contacts, it’ll take you several months.

But it doesn’t have to be this way.

If at any point you want to scale up your outreach, you can if you have multiple email addresses warmed up and ready to go.

Even if you only have a list of 1,000 contacts this month – if you suddenly did a lot of prospecting and found a bunch of new opportunities, having multiple email addresses warmed up would allow you to reach those contacts quicker and not have to be waiting.

Have an Immediate Backup Ready to Go in Reserve

Don’t have all your eggs in one basket!

What happens when the unthinkable happens, and your email address ends up on a blacklist?


Your emails are all going to spam folders and you’re burning through all your contacts.

You need to stop using that email address immediately and then:

  • A) work on rehabbing it to improve its deliverability (which can take from a few weeks to a few months to do); and
  • B) start using another email address in the meantime that has good deliverability.


But, if you don’t have an email address warmed up and ready to go, then it’s going to take you several weeks to warm up a brand new email address.

You put all your eggs in one basket with that one email address, and now the eggs are cracking.

With a new email address that you’re warming up, it should be exclusively on warm-up mode for 3-4 weeks before you start using it for cold emails.

That means no cold emails with that email address for 3-4 weeks.

So during this time, you’re losing several weeks where you can’t send cold emails. And that can kill your sales pipeline.

So, the relatively small cost of having another email address and warmup provides insurance in case your email address gets burned and starts seeing deliverability drop.

How Many Emails Should I Be Warming Up?

Now, let’s answer the question we posed at the beginning, “How many emails should you have warming up?”

The answer is: No fewer than two.

If you are only planning to send 500 – 1,000 emails per month, and you’d only need one inbox to send from – you should have one backup email address warming up just in case that first email sees its deliverability drop.

If you want to really play it safe, you can have a backup for each email address.

So, if you’re sending 5,000 emails per month between 5 inboxes, you could have 10 emails warming up – 5 for sending, and 5 in reserve.

But, is it likely you’ll need to swap in 5 email addresses at once?

Probably not.

So, here’s a little chart I made up to give you some ideas for how many email addresses you’ll want to have in warmup at a minimum based on the volume of emails you’re sending per month:

Emails sending per month Total email addresses needed to send this quantity of emails per month # of email addresses to have in reserve # of total email addresses to have in warmup
0 - 1,000
1,001 - 2,000
2,001 - 3,000
4,001 - 5,000
9,001 - 10,000


Having multiple email addresses warming up ensures that you are able to send your emails safely, without having to worry that your cold emailing will be stalled if you run into any deliverability issues with one of your email addresses. And, having multiple email addresses warming up ensures that you can send a greater volume of cold emails.

Email Deliverability FAQs

Still have questions after testing your email deliverability?

If you’re using a brand new email address, we recommend sending to more than 2-5 emails per day for the first 5 days. Then you can increase by 3-5 emails per day.

Using a solution like Boxward allows you to see your email deliverability over time including, inbox rate, categories (updates/promotions tabs) rate, spam/junk rate.

Using an email warmup network like Boxward ensures that your emails are engaged with in a positive way – opened, marked important, replied to, and moved from spam/junk to the inbox when necessary.

Start Warming Up Your Email!

You could be losing sales right now with emails landing in junk