Email Spam TestImprove Your Email Deliverability: The 18 Actions (2025)Uncover the secrets to enhancing your email deliverability with our 18 proven solutions for 2025. Drawing from 5 years of intensive cold emailing and managing deliverability for over 130 companies, we offer insights grounded in real-world experience and data.
There are plenty of guides about deliverability and on how to improve email deliverability. We know that.
Most guides give the same obvious or incorrect advice and don't give the most efficient strategies, tips and techniques.
Why? Because very few people and companies truly understand deliverability and specifically cold outreach deliverability.
This guide is the result of :
The guidelines we give in this guide are the ones we used to :
In other words, we master the email and deliverability game and precisely how to improve email deliverability and understand why your emails are going to spam.
That's precisely why we decided to work on the most efficient email deliverability solution, composed for now of an email warm up tool and a spam test.
Of course, as deliverability constantly evolves, we're going to update this guide as often as necessary.
We hope you're going to find really helpful tips to improve your email results.
Nearly nobody mentions this.
To pass the spam filters, all domains and TLDs are not equal in terms of deliverability, at least to start.
By making the wrong choices on choosing your sending domain, you can start with a handicap.
Some domains and extensions (TLDs) are more associated to spam than others.
A spammer keeps burning domains because his sender reputation and deliverability is constantly dropping.
That's why his most common behavior is to keep buying new domains and sometimes, a lot.
To get plenty of domains, a spammer has to be creative with the name, like using hyphens (e.g. “company-team.com”), numbers and buy all the exotic extensions : “.xyz”, “.biz”, “.website” etc.
Thus, when you select a email domain to send your email campaigns from, be careful not to choose one that can already be considered suspicious.
When choosing the domain name :
Which domain extension to choose :
For more info on bad and good TLDs, check the Spamhaus TLDs statistics here.
Bonus tip : women have higher open and reply rates on average than men. Surprising, isn't it ?
Quick reminder :
SPF = Sender Policy Framework
DKIM : Domain keys identified mail
You may have read it everywhere but you have to do it, that's mandatory to prevent emails from going to spam.
Here's how to properly set up SPF and DKIM records
DMARC is not yet mandatory, you can have a perfect email deliverability without it but it may become more important in the future so set it up :
Having your own custom tracking domain is crucial, you absolutely need one. A real must have.
Let me explain why concretely so you understand it well.
When you use an email sending / automation tool for your campaigns, your emails are sent with a tracking pixel associated to an URL inside the body (in the HTML). It's added by default.
This tracking allows you to know your open rate and click rate. And, of course, that's useful to check the results of your campaigns.
This tracking code is always associated to an ip address, an URL, a domain.
And by default, this domain is shared between all the customers of the sending tool you use.
The problem is : if you don't set up your own custom tracking domain, your own marketing emails will be associated to all the customers of your sending tool who did not set up their own custom tracking domain.
What does it mean ?
It simply means that if you have the same tracking domain as potential big spammers your marketing emails can be identified as spam.
In short, to prevent emails from going to spam, you don't want to be infected by the bad behavior of others.
By setting up a custom tracking domain, you isolate yourself from others and build your own sending reputation.
Most email sending services allow you to set up your own tracking and email domain. Look for this feature, check in the documentation or ask it to the support team.
If they don't allow that option, switch to another sending and reliable email service provider.
[B2B Cold Outreach Use Case]
Google Workspace (Professional Gmail) and Office 365 (Exchange) are the top 2 email service providers to land in your recipients inboxes according to our data.
All the other ones offer a much lower deliverability.
And that makes total sense: Google and Microsoft own most of the mailbox market.
Who's better than a Gmail or an Outlook address to land in the inbox of a Gmail or Outlook mailbox?
Choose one of these 2.
Once it's done, you can use an outreach solution that will automatically send your email sequences from your inboxes.
We recommend Emelia, Apollo, Reply.io, Outreach.
This one is a game changer.
If you're doing cold outreach, don't send more than 100 cold emails per day per email address and ideally per email domain.
Remember the #1 rule : have a human behavior.
A real human being who use his little hands does not send 2 000 marketing emails per day. Or he's super fast. You understand.
From all the tests we've done, the fewer emails you send per day, the better for your sender reputation and deliverability.
So if you can send fewer per day per email address / domain, do it.
Tip : these numbers are only for your campaigns emails, they don't include the warming emails.
If you need to send a higher volume per day, follow these guidelines.
To learn more on this, we have released a step by step guide on the absolute best cold email deliverability sending strategy.
The difference on your sender reputation's trend without and with email warm up.
A lot of people think email warm up is important ONLY BEFORE sending email campaigns.
A one shot warm up done only before sending is not enough to maintain a great deliverability and good sender reputation over time.
You have to constantly warm your email account, before, during and between your campaigns.
We have written a dedicated article on the subject : Why to Always Keep Email Warming to Maintain a Great Deliverability
Let's explain this.
Getting a high engagement rate, having a lot of positive email interactions (having your emails opened, clicked, replied, marked as important, removed from the spam folders), is one of the strongest factors to build a positive sender reputation and avoid the spam folder.
And that's logic : if a lot of people open your emails, reply to them, mark them as important, that means your emails are interesting.
Big email service providers such as Google and Microsoft Outlook take that into account.
Gmail uses engagement as a factor for filtering your email."
SendGrid: “The higher your email engagement, the more likely you are to avoid spam filters and land in the inbox.”
CampaignMonitor: “Now, whenever you send a new email campaign, email inbox providers, like Gmail and Outlook actually look at their user engagement and previous interactions with your past campaigns. They then use this information to determine whether your latest campaign makes it to the inbox or not.”
If you don't have a constant email warming activity, you need to have an offer, a subject line and an email copy that everybody loves. This way, you'll have plenty of positive engagement on your emails.
But, unfortunately, that's nearly impossible.
Also, when you're sending email campaigns, you will have a certain proportion of your emails being marked as spam. Each times it happens, it badly hurts your sender's reputation, reputation and deliverability.
A constant warming will help you correct this and balance your activity
On top of that, having a linear activity is also crucial to improve email deliverability.
Not sending email during 2 days, then sending 300 emails, stopping for 1 day, send 200 emails, stopping for 2 days, etc. is bad.
You want a linear activity, with constant positive engagement. This way you're going to build a strong email deliverability in the long run.
This is exactly why we've created MailReach after spending 5 years of sending cold email campaigns, fixing deliverability and reputation problems.
MailReach helps you reach the inbox and stay there by constantly generating engagement to your sending addresses and domain, and optimize your email content to pass the spam filters with a powerful spam checker tool.
Again, remember the #1 rule ? Let's say it again : have a human behavior
A human does not send big email blast to thousands of people in one second.
Setting a delay between each email helps a lot to land in the main inbox and get high open rates.
Now, proper cold email automation tools send emails with a delay.
To test your email deliverability, get your spam score and find out where your emails land on the major internet service providers', you can use MailReach's Free Email Spam Test
Most of the other spam checkers are biased or not reliable to properly measure your inbox placement.
You simply have to send an email (under your real sending conditions) to a list of 30 inboxes given by MailReach and we'll give you a detailed report on your email deliverability including all the things you can improve to land more in inbox.
You get a score out of 10 and a list of checks (content, spam words, links, tracking, blacklists and many more).
Do it, that takes one minute and that's the best way to measure your inbox placement.
[B2B Cold Outreach Use Case]
Below, you'll find the characteristics of a high opening email list.
To get high open rates and overall great cold email results, you have to be picky with your email lists. That's important to prevent emails from going to spam. If you need more tips check out our Cold Email Deliverability guide.
When you send your emails, that's very important that you reach out to a particular person each time, not to generic email addresses like contact@xyz.com (except if you know this address is associated to one person only).
Sending emails to generic email addresses is generally bad for deliverability.
First, because it's harder to personalize an email sent to a generic address. No, you're not going to write “Hi Contact, I hope you're doing great”.
Secondly because it can badly hurt your email deliverability.
When you send an email to a generic email address, your email is most of the time redirected to different people inside the company. Sometimes to dozens of people.
As it's less personalized, the risk of being marked as spam is multiplied.
And spam complaints hurt a lot, especially in 2025. You need to minimize this risk.
That's important to personalize your content and, as a result, lead to a better email deliverability.
Personalization is crucial, not only to increase your lead, click or reply rate but to make sure you're sending a “different” email content to each recipient.
Sending the same email content to hundred or thousands of contacts is a spammy behavior, you don't want that. Doing this will most likely raise the risk to land in the recipient's spam folder.
That's why it's very important that you personalize your emails with at least the name of the recipient. “Hi [First Name]” is the minimum, do it.
Bonus tip : using the company name of your recipient's primary inbox in the first sentence of your email increases your reply rate.
That's simple, your list must contain people who can be interested by your product or service.
Of course, you can't really guess if John will buy your product before contacting him. But John has to be in the target.
Let's take an example :
You sell fund raising services to startups and small companies. You want to reach out to relevant companies that can be interested to raise funds with you.
When you're working on your email list, you have to make sure it effectively contains CEOs / Founders of startups and small companies that CAN raise funds.
That means :
If you send irrelevant emails to someone who's absolutely not in the target, it will :
We won't chit chat during hours, the best source of high quality contacts is LinkedIn.
Here's why:
We've tested many tools over the last 5 years doing cold outreach for a lot of companies and ourselves. The tools below are the best in terms of easiness, speed, data quality and number of emails found.
Having access to quality emails and data is cool. But once you get the list, it's not finished.
You still have work to do if you want to get the best results from your emails.
Spending time on your list is a key factor to maximize your campaigns results (which require the best deliverability).
This is the list of actions you need to do to before going to the next step :
By doing these steps, you'll improve the quality / relevance of your list, minimize errors and reduce the risk of irritating people and having your emails reported as spam
A great help to prevent emails from going to spam.
You may have read that before. You have to verify your email list before sending your campaigns.
By verifying we mean checking the validity of the email addresses in your list and removing the ones that are not valid.
Let's see how to do it the good way.
Which tool to use ?
There's plenty of tools that verify email lists. We've compared a lot of tools and our top picks are Verifalia and DeBounce but if you still want to compare, this article did a nice summary.
How to filter your list based on your verification results :
There are usually three main verification categories : Success, Risky and Undeliverable.
Success is the best but it does not guarantee a 0% bounce rate.
Risky contains mostly Catchall emails and emails which encountered verifications errors (timeouts, etc).
‘Catch all' are emails that you can't know if they're valid or not. That's a bit like the lottery. But we know from studies we've made that around 20% of catch all email bounce. Keep in mind this number.
Undeliverable are the invalid email addresses : the bad and ugly ones.
Here's what we recommend to follow to protect and maintain a great deliverability.
First, exclude all the undeliverable emails. That seems obvious but do it.
At the beginning, when your domain and your email account is new and you're doing your first campaigns, we recommend to target exclusively the “Success” ones. It will minimize your bounce rate and you don't want to have a high bounce rate especially if your email account / domain is young (less than 3 months).
When your email account gets older, we recommend adding catch all emails in your campaigns but the hack is to cap the percentage of catch all emails to 25% max of your list. The remaining 75% are the emails that are Success.
This way, you have more control on your bounce rate.
The worst thing to do for your email reputation is to send big loads of emails to catchall email addresses only and get a lot of bounces.
Remember the rule, you want to have the lowest percentage of bounces on your email account. Aim less than 4%
Personalizing your emails helps you increase your campaign results : open rate, click rate, reply rate and lead rate.
Beyond that, it's plays a strong role regarding email reputation and deliverability.
When you personalize, you don't always send the same email
And Google, Microsoft and any other email service provider understand that you have a minimum knowledge of your recipients.
Remember to always act human. A real human is not likely to send the exact same email to 1000s of people each day.
By personalizing email authentication, we mean using the name of your recipient (first name and/or last name) and if you can, their company name.
This helps to pass the spam filters.
To pass the spam filters and avoid landing in the junk folder, you absolutely have to avoid the following :
Spam trigger words : they're not always the ones you think. You don't have to talk about viagra, sex or increasing the size of your penis to land in the spam folder. There are plenty of others you're not aware of.
For instance, let's say that tomorrow, nasty spammers start sending massive spam containing the word “Crypto” and a lot of people report their emails as spam. “Crypto” can then become a spam word because spam filters / algorithms have associated this word to spam. Understand?
That's how modern spam filters work to identify spam words.
Aggressive punctuation : typically, avoid the “!!!“.
Capital letters : NO, DON'T WRITE LIKE THIS, LOL. That triggers spam filters.
Attachments : sending attachments is associated to phishing and hacking. Don't send any attachment when sending cold emails, never. That's one of the best ways to trigger spam filters.
Links : the fewer links in your email, the better. If you really need to send a link, make sure the website is https secured (to check it, open the website in Chrome and check if you can see the little padlock on the left of the URL). There are many links associated to spam. We've seen tons of time people land in the spam folder just because of one link in their content, beware !
Too much image content : the less image, the better for your email deliverability. Yes, you can remove your fancy logo in your signature, it can only be better to prevent landing in the spam folder.
Too much HTML formatting : the less formatting, the better. Remember, your email has to be as human as you can. A human does not use complicated HTML when he sends an email. The HTML code has to be the lightest possible with minimum formatting.
In all cases, we strongly recommend you to use our email spam test that allows you to test your deliverability and see exactly where it lands on dozens of inboxes. It gives a huge help to craft emails that passes the spam filters and land in the recipient's inbox.
Spam complaints are a deliverability killer. Investing time to learn email copywriting and please your recipients will help you increase your your email delivery and results, including avoiding the spam folder.
One of the top causes of a spam spike/reputation drop is because of complaints.
And people can mark your email as spam for different reasons :
That's why you must be careful, nice and as delicate as possible. Don't be a cheap vacuum cleaner vendor.
These are our guidelines :
A nice hack can be to ask yourself “How I'd like to be contacted, if someone wanted to email me to sell me the same thing I'm offering?”
Besides the question of being compliant with the CAN SPAM ACT, we see there's still people debating between including or not an unsubscribe link in your emails.
Some people say it's better not to put one because it makes your email looks automated and then less human.
Anyways, there's no debate anymore for us at MailReach. Including a link to unsubscribe equals having a better email deliverability, period.
If you don't have an easy-to-spot link, people will click on “Mark as spam”, that's it. Even if you've said You can unsubscribe by replying “Unsubscribe” to this email.
When people are irritated by your email (and it always happen to at least some % of your list, even for the best of us), they don't give a sh*t about replying “Unsubscribe” to your email. They just want to ban you of their life, as soon as possible.
To conclude, include an unsubscribe link at the end of your email to minimize the number of spam complaints. Don't play with that. And it's better to be compliant with the CAN SPAM ACT.
If you have read the whole guide, you can easily understand that email deliverability is now a skill, a job or even more, a science compared to the golden age where you could just send email campaigns and have great open rates.
Keep in mind that an imperfect email deliverability means missing customers and revenue. Never neglect it.
You have to be rigorous on following the best practices, get help from the right email deliverability tools like MailReach (yes that's us 😎) to expect and maintain the best results in the long run.
Et voilà like we say in France, we hope you've learned at least some very concrete and valuable tips to boost your results.
