2022 Guide To Reaching Your Customers’ Inbox


Email deliverability is the rate of outgoing emails and how many reach the primary folder of the recipient inbox. If your email has a low deliverability rate, it will have a high chance of landing in the spam folder (which you obviously don’t want). As you can infer, an email with high deliverability will make it to the recipient’s inbox. For sales teams as well as for marketers, deliverability is a key indicator to estimate the efficiency of a cold emailing campaign.

Because email deliverability affects the efficiency of your email marketing strategies, it is crucial! Any marketing campaign such as newsletters, product descriptions, cold outreach campaigns, or transactional emails all need to be delivered in the inbox.

If your email lands in spam, then it won’t be opened nor read. End of story. Low open rates, low engagement, and low email deliverability all lead to horrible ROIs. This is why you need to have as high as possible email deliverability.

Email deliverability is broken down into 3 parts: sender reputation, inbox activity, and email content.

What is sender reputation and how to improve it?

Sender reputation refers to the trust  “score” given by ISPs (Internet Service Providers) to domains and IPs that send emails. The higher it is, the higher the email deliverability rate. If it’s low, ISPs will consider your domain/IP as suspicious and your emails will land in spam.

Sender reputation can be difficult to understand, to evaluate. Having an idea of the state of your sender reputation and how it impacts your campaign’s performances can be very valuable for you and your business.

You can use tools like “Warmbox” Inbox Spam Checker”, to your sender reputation and identify what’s wrong with it (IP/Domain blacklists, Reverse DNS, SPF, DKIM, DMARC, etc.).

Such a tool will provide you with a deliverability score as well as a complete report, detailing what’s wrong with your inbox.

What is inbox activity and how is it used?

Similar to your sender reputation, inbox activity is the history of your email address and is used by spam filters to determine your email deliverability.

The best way to reach the maximum deliverability is by having an active inbox with regular and healthy records. 

Here are some tips for inbox activity:

    1. Warm up your inbox before sending
    2. Maintain steady email activity, avoid huge gaps in sending volume
    3. Respect your ESPs sending volume limitations
    4. Limit bounce rate by regularly cleaning your list
1). Warm up your inbox before sending

Email warm up consists of gradually increasing the number of emails sent by an inbox and generating interactions with these emails (getting opened, replied to, marked as important, etc).

This process helps increase email deliverability (i.e. the ability to land in the inbox instead of spam) of the email address. Thanks to the email warm-up, ISPs will identify you as a good sender and won’t put your outgoing emails in spam. 

All these actions can be performed by human beings, but can also be automatized using softwares such as . In that case, the warming inbox will interact with other inboxes to reproduce human behavior, with the objective to improve its deliverability.

There are usually 3 types of users for whom email warm up can help tremendously:

        • Newly created emails/domains that are just starting out. It is a great idea to generate some email activity with a high level of engagement to warm up the inbox and make sure that the first outreach campaigns launching from this inbox have the best deliverability and engagement possible.
        • Inboxes with damaged reputation cause by spam history can use email warm up to recover your reputation and make your email deliverability good again.
        • Inboxes with decent deliverability that just want to improve it to the maximum possible. In this case, email warm up helps maintain your deliverability rate so it doesn’t drop.
2). Maintain steady email activity

Having a perfect email activity means avoid suspicious gaps in your daily sending volume. It sounds basic but it’s the core of the issue.

This is why it’s crucial to keep your sending volume as steady as possible over time. This can be easily achieved thanks to email sending tools that enables you to set up your campaign’s sending volumes on daily basis.

In the same spirit, if you plan to increase you sending volume, to do cold outreach for example, it’s important to increase your daily sending volume progressively. To avoid huge gaps in your inbox activity and make sure your emails won’t land in spam.

3). Respect your ESPs sending volume limits

All ESPs allow you to send a limited amount of emails every day. Above this limit, additional emails won’t be delivered. And worse, if you’re playing too much with the limits, your ESPs can devalue your overall email deliverability for excessive volumes.

The best is to be aware of the limits related to your ESP before starting a mass emailing strategy.

It can be also a good call to check what email service provider best fits your need in terms of sending limits.


4). Limit bounce rate

Bouncing is one of the worst thing that can happen to your emails besides landing in spam.

In email marketing, a bounce correspond to an email that has not reached the recipient. At the difference with spam, that reached the recipient but not the inbox, a bounce won’t be present at all in the recipient inbox.

An email will bounce if:

        • The email address of the recipient doesn’t exist.
        • The domain of the recipient doesn’t exist.
        • The email address of the recipient doesn’t allow to receive emails.
        • The inbox of the recipient is full.
        • The email message sent is too long.
        • The receiving server is down.

You should avoid bounce for two reasons.

An email that bounces won’t reach it recipients at all. And as for spam, it won’t generate value as it won’t be read. If your emails have an extremely high bounce rate, your inbox reputation can decrease, and affect your overall email deliverability.

The best way to reduce your bounce rate is to keep your mail list as clean and fresh as possible. Create dynamic segments in your ISP for emails that bounce more than once and exclude them from future campaigns. 


How to make sure your content isn’t flagged for spam

Besides the reputation of the sender, spam filters also take into consideration the content of the email itself. They use basic verification points to identify easily scams and spam attempts. And in the same way, the final recipient of your message will also act as a spam filter, reporting your email as spam, if the content is not relevant enough, or appear as spam to user.

It’s important to note that having too many people reporting your emails as spam can have a very negative impact on your deliverability as a whole, as it also impacts your sender reputation. This is why, regarding your email content, you have to be careful about both about the analysis of spam filters (basically robots), but also to the perception of people that will receive your emails.

Follow these simple tips when it comes to the content of your emails:

– Avoid using spam-trigger keywords in your emails (subject and body). A simple google search will bring up multiple articles outlining all of these words you should avoid.

– Personalize your emails so your recipients find your email interesting and not spammed. In addition, poorly personalized and irrelevant content won’t provide value nor conversions.

– Avoid sending heavy attachments in your emails as it can be considered suspicious/dangerous activity. If you need to share a large file with your recipient, we recommend using a Google Drive or Dropbox link.

– Include “unsubscribe” link in your emails so that your recipients do not have to mark your email as spam. Many ISPs will actually ban you from using their services if you receive a large amount of “marked as spam”, so please do this.



To wrap up this lengthy guide, email deliverability mostly relies on the implementation of good email practices, combined with an effective warm up and proper content strategy. Dissect your current email marketing campaigns and utilize the information laid out in this guide to build/maintain a high email deliverability rate.

If you have any questions, please feel free to reach out to us or by email at

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