Cold Email Deliverability : The Ultimate Guide (2025)

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Why do we feel legitimate writing this email deliverability guide ?

As usual, to give credibility to what we’re saying, that’s important to mention our experience in the email field and especially with cold email deliverability.

We have been sending cold emails for 5 years for 130 companies in 40+ different industries and keep doing it. This is crucial to develop a service that is really efficient and brings a lot of value to raise your cold email deliverability.

Our track record :

• Grew from 0€ to 120k€ Monthly Recurring Revenue in 6 months in our previous company with cold emailing as the only acquisition channel.
• Helped raise 56M€ in funding for IPOs and seed rounds with cold emails in France.
• 75% open rate on average for > 130 companies sending thousands of cold emails per month.

We faced so many cold email deliverability problems and lost so much money because of that, you can’t imagine.

In other words, you can count on us for cold email deliverability.

The context: maintaining a good cold email deliverability is much harder than before.

Cold emailing is very different from sending emails to people who subscribed to your list. The risk to land in spam is much higher. Cold email deliverability is then more difficult than opt-in email deliverability.

Why ?

Because you are reaching out to people who don’t know you and didn’t ask for your emails. And a certain percentage of them will mark your emails as spam, even if you offer the best product or service.

That’s the hard truth and it happens to the best cold emailers.

The problem is that, in 2025, having your emails marked as spam has a very negative impact on your sending reputation and deliverability. Way more than before.

It hurts your cold email deliverability because the major inbox providers such as Google and Microsoft have added more weight on the action of reporting spam and on the engagement received on your emails.

That’s why today, if you need to send more than 100 cold emails daily with a good cold email deliverability and open rates in the long run, you need several sending addresses with different domains, period.

There’s no discussion on that, except if you want to have bad results, but who wants that?

This is why to have a good cold email deliverability and great results from your campaigns, you need to put in place the right sending tactic. Keep reading.

The Multi Sender tactic : the most efficient sending and warming strategy for a perfect cold email deliverability.

#1. Send MAXIMUM 100 cold emails daily per sending address to maintain a good cold email deliverability.

One of the golden rules of cold email deliverability is to have the most human behavior possible. The behavior of an interesting person who sends emails and gets a lot of engagement (emails opened, replied, marked as important and removed from spam).

We’ve found from our tests and data that 100 cold emails daily per sending address and domain should be the maximum to have and maintain a good cold email deliverability. The fewer the better. If you can send 80, do it.

If you exceed 100 cold emails daily per sending address, the risk of having spam issues is much higher. That’s up to you to take this risk and we don’t recommend that.

From our experience, the ROI is much better when sending less than 100 emails per sending address and have a better cold email deliverability than wanting to send more and deal with spam issues and all the pain in terms of business.

#2. Minimize the number of sending addresses per domain (1 is the best) to reduce spam risk, avoid spam contamination and maintain your cold email deliverability.

Generally, people don’t like this one.

What?! I need to buy several domains ? But I have one, why it’s not enough ?

That’s an easy answer : if you have 3 sending addresses BUT they’re all on the same domain it’s the same as sending 450 cold emails from one domain.

It makes you send more emails per domain so it increases the risk to land in spam and accelerates the fall.

So basically, it will make you land in spam faster AND, when the first sending address will be flagged as spam, the other ones will be affected and start landing in spam too since they share the same domain. Wasted. You’re dead.

Don’t put your all your eggs in the same basket, that’s taking a big risk for your cold email deliverability

1. Buy several domains (read our Ultimate Deliverability Guide for the best practices).

2. Set up one sending address per domain.

Two benefits :

– Better cold email deliverability since you send fewer emails per domain.
– Lower risk of spam contamination between your sending addresses and domains.

We’ve learned that one the hard way, save time and money, follow this advice.

#3. Warm each sending address with MailReach and/or have a warming activity that represents at least 15% of your sending volume.

When using MailReach on autopilot mode (by default), the daily volume of warming emails is around 50, which is perfect to have a great engagement rate on each of your sending address.

By using a good email warm up tool (read our MailReach vs other solutions 😉) you’ll get a perfectly balanced email activity to maximize your cold email deliverability. A lot of engagement : people opening and replying positively to your emails, marking them as important, removing them from spam when needed, etc.

Also, you’ll benefit from our smart warming algorithm that constantly adapts to maximize your deliverability and maintain it in the long run.

Conclusion

Using the Multi Sender strategy with a smart email warm up service can by itself fix a lot of cold email deliverability issues faced by companies.

This is one of the major discoveries we’ve had when working and sweating over deliverability issues in the past.

Make good use of it because a great power comes with great responsibility 🤙