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Email deliverability: understanding, measuring, and optimizing your marketing campaigns

In the competitive world of email marketing, deliverability is not just another performance indicator; it's the cornerstone that determines the success or failure of your marketing campaigns. Understanding email deliverability, measuring its impact, and optimizing it are therefore essential skills for marketing and CRM managers and operators. This article delves deep into these aspects to help you maximize the effectiveness of your email marketing campaigns.


What is email deliverability?

Email deliverability is the ability to reach your recipients' inbox. It's an important measure of success in email marketing.

For webmail, email deliverability is the percentage of emails that reach the recipient's main inbox, excluding emails that end up in the promotions tab or the spam folder.

However, a small clarification is needed. Did you know that there's a difference between email deliverability and email delivery?

Why email deliverability and not email delivery?

Email delivery involves successfully sending an email to a recipient's server. It doesn't distinguish whether the email arrives in the main inbox or the spam folder. Therefore, it's entirely possible to have a high delivery rate but low deliverability.

For this reason, let's focus together on email deliverability and how to improve it.

Why is email deliverability important?

In the world of email marketing, tracking your emails' deliverability rate is crucial for several reasons:

Reason No. 1: Knowing if your recipient has received your email

One of the primary reasons to track the deliverability of your emails is to check if your newsletter subscribers have actually received your emails.

Marketers are interested in this measure to identify:

  • Their most active subscribers.

  • Factors affecting engagement.

  • Recipients who do not open emails.

Reason No. 2: Measuring your recipient's engagement

Having a well-stocked subscriber database is great! But if these contacts do not open or click in your emails, you might face some difficulties in achieving your marketing and business goals.

The lack of engagement from your subscribers will heavily impact your deliverability and, consequently, your reputation. Unengaging content is considered spam by webmails. Your messages will be filtered, including those sent to engaged subscribers.

Therefore, monitoring your subscribers' engagement is crucial. At Actito, for example, we offer an engagement scoring module. This engagement score is represented by a visual gauge that allows you to measure at a glance how engaged each profile is with your brand. This score helps distinguish between highly engaged profiles (who could benefit from a reward program) and disengaged profiles (who should be targeted with a reactivation campaign).


Reason No. 3: Improving the campaign in the future

Email deliverability helps marketers understand:

  • Unsubscription and complaints

Unsubscription allows us to identify a message that generates some dissatisfaction or too much marketing pressure.

A complaint is a report made by recipients indicating that the message is spam.

Some webmails offer a feedback loop service that generates an email, allowing Actito to identify the complainant and blacklist them.

  • Engagement and responsiveness indicators

These two indicators help identify what works, thereby improving reputation because it's a positive point for webmails.

How does email deliverability work?

Understanding the journey of an email

STEP 1: Sending the email

The sending of an email starts by establishing a connection between the sending server (email sender) and the recipient's mail server. If the sender practices poor habits and therefore has a bad reputation, the connection is halted. The email will be rejected (bounce). Thus, there can be a blockage and a deliverability issue without the email even being sent.

STEP 2: Delivering the email

Next, the email is delivered.

If your email is rejected, it is considered a bounce. At Actito, there are 3 types of bounces:

  • Hard bounce: the email could not be delivered because the address or domain does not exist (the domain server replied that the address before the '@' does not exist).

  • Spam bounce: the email was not delivered due to the sender's reputation or failure to adhere to best practices. This type of error will pause sending attempts to retry a little later. For example, if you usually send 200,000 emails per day and you send 250,000 on a given day, it's likely that the additional 50,000 emails will be rejected as spam bounces.

  • Soft bounce: the majority of soft bounces are due to full mailboxes or pending messages that could not be delivered.

STEP 3: The email arrives in the inbox

The webmail then checks the content of the message (HTML code, links, spam words) to determine where it will deliver the message: inbox, spam folder, or trash.

As a reminder, some webmails have set up tabs to facilitate users' access to important emails (Gmail / Hotmail).

There is no technique for landing in the Priority tab for email marketing and the fact that your promotional messages land in this tab is not a mistake or a punishment.

Your recipients are used to this and if they wish to receive your messages in their Priority tab, they can decide freely. Gmail takes a very dim view of any circumvention tricks and can impose severe penalties.

The Promotions tab can also be used to highlight certain emails that correspond to the recipient.


Gmail offers a tab dedicated to transactional emails (Notifications) to make life easier for their users. In order for your transactional emails to be properly classified, they must be sent using a dedicated domain.

STEP 4: The recipient opens the email, or not

The fourth step is whether or not the recipient opens the email. This depends on the relevance and appeal of your subject line.

Beware, Apple has made this metric unreliable since iOS15. Apple will register systematic openings, which obscures the signal.

For this reason, Actito no longer counts iOS15 openings (only clicks are counted on Actito).

STEP 5: The recipient's action

As the last step, the recipient may take one of the following actions:

  • Click on one of the links in your email.

  • Unsubscribe from your newsletter.

  • Mark your email as spam.

Clicks will positively impact your reputation because the webmail will understand that the recipient is interested.

Unsubscribing is considered a neutral click.

However, if the recipient declares the email as spam, this will negatively impact your reputation.

Some webmails offer a service to collect complaint information (feedback loop) which is processed by Actito (the email is blacklisted and will no longer be contactable).

Webmails that offer the feedback loop include Hotmail, Yahoo, La Poste, SFR, etc.

Why are your emails delivered to spam?

Anti-spam filters play a crucial role in managing incoming emails by identifying and blocking unsolicited or malicious messages. Understanding why your emails might be marked as spam is a prerequisite for improving your deliverability and ensuring your important communications aren't ignored or rejected.


Server anti-spam filters

Email servers use a variety of techniques to assess the legitimacy of incoming emails. It's important to understand that their primary role is to protect recipients from spam and attacks (phishing, ransomware, etc.). They examine different elements such as the email's subject line, the sender's IP address, the content of the message, and any included links. If an email is deemed suspicious or non-compliant with the server's security policies, it can be automatically filtered into the spam folder or even have its reception refused. This will then generate a Spam bounce on Actito.

Arrival at the recipient's server

Once the email is accepted by the recipient's mail server, it undergoes additional filtering rules. These rules may include checking the sender's reputation, scanning the email content for keywords associated with spam, and comparing against blacklists of IP addresses known for sending spam.

Passing through the client's anti-spam

Some users also have anti-spam filters set up at their email client level. These filters can be more or less restrictive based on the user's preferences. If your email is marked as spam by the client's anti-spam filter, it might never be seen by the recipient.

What affects deliverability?

To prevent your emails from being delivered to spam, ensure you follow good email marketing practices, such as using a clean, opt-in mailing list, personalizing emails, avoiding suspicious keywords, and monitoring your sender reputation. Additionally, make sure your emails are correctly authenticated using protocols such as SPF, DKIM, and DMARC, which will strengthen trust in your domain and reduce the risk of being classified as spam. By taking these proactive steps, you can improve the deliverability of your emails and maximize the impact of your marketing campaigns.

The sender's reputation

Reputation is paramount in email marketing as it can have a direct impact on how your emails are received by your recipients. When you send an email, webmails perform a reputation test to evaluate your credibility.

If your reputation score is high, your emails are more likely to land in the recipients' main inbox. Conversely, if your score is low, your emails may be directed to the spam or junk mail folder.

How to improve your reputation?

  • Send your emails consistently and regularly.

  • Contact only active and engaged addresses.

  • Avoid contacting inactive or ghost addresses to prevent an increase in the bounce rate.

  • Avoid spam traps.

  • Stay off blacklists.

  • Work on your content and the relevance of your messages.

⚠️ Your reputation greatly depends on the behavior of your message recipients today. The more your recipients show strong interest in your messages, the better your reputation will be. Conversely, any sign of disinterest will penalize your reputation. It's therefore important to contact only engaged addresses to build and sustain a good reputation. Email is a link with your customers, and you want to give them a good image of your brand. This also means contacting them only on topics that may interest them.

Below is the new email activity report in Actito, which can be useful for checking the quality of addresses.



Maintaining a high-quality email infrastructure can be complex and costly. That's why it's recommended to use a service provider to manage your infrastructure.

Here are some factors to consider to maintain a good email infrastructure:

  • IP Address: If you're sending a large volume of emails, it's important to carefully manage your IP address. Using a dedicated IP address, like those offered by Actito, can help preserve your reputation.

  • Feedback loops: If a recipient marks your email as spam, it's crucial to remove them from your database.

  • Sending speed: Each webmail has different reception capacities. Local email servers like those of La Poste, SFR, or even Orange, do not have the same reception capacity as webmails such as Gmail and Hotmail. Therefore, it's necessary for your router to adapt sending speeds to avoid overloading the recipient's email servers. Too fast sendings can indeed generate connection refusals which increase the bounce rate.


Authentication is a process aimed at verifying your identity (via your IP address) and the validity of the messages sent. This ensures that the emails received actually come from you (and not another entity) and are authentic.

Authentication protocols, such as SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting, and Conformance), are essential for strengthening trust between sending and receiving servers.

  • SPF (Sender Policy Framework): SPF is a validation mechanism that allows email servers to verify if an email comes from a legitimate source. It works by enabling domains to specify which servers are allowed to send emails on their behalf. SPF authentication helps prevent falsified email address and reduces the risk of spam.

  • DKIM (DomainKeys Identified Mail): DKIM is a technology that adds a cryptographic digital signature to each outgoing email. This signature is associated with the sender's domain and verifies the email's authenticity when received by the recipient's mail server. DKIM authentication helps ensure the integrity of emails and strengthens trust in their source.

  • DMARC (Domain-based Message Authentication, Reporting, and Conformance): DMARC is an authentication policy that builds on SPF and DKIM to protect domains against email spoofing. It allows domain owners to specify how unauthenticated emails should be treated by mail servers and provides detailed reports on email authentication activities. DMARC authentication enhances email security and helps organizations better control their online reputation.



When creating your emails, it's crucial to consider the content you include, as it can significantly impact deliverability. Here are some aspects to consider:

Text and spam words

As mentioned earlier, anti-spam filters scan your email's text for words or phrases often associated with spam. Avoid using suspicious words or sensationalist expressions that could trigger anti-spam filters. Instead, opt for clear and professional language that effectively communicates your message without raising the suspicions of filters.

Domain names and URLs

Using suspicious domain names or URLs redirecting to unsecured sites can also harm your emails' deliverability. Ensure your links point to legitimate destinations and avoid URL shorteners that can mask the destination's identity.


Emails containing only images without text can be perceived as suspicious by anti-spam filters, as they're often used by spammers to bypass undesirable content detection. Ensure to include a balance between text and images in your emails, and use ALT tags to describe the content of images for recipients who cannot see them.

HTML code

Poorly formatted HTML code or containing suspicious tags can trigger anti-spam filters. Ensure your code is clean and valid, and avoid including deceptive practices such as hidden text or content obfuscation techniques.


Webmails take into account the behavior of recipients to gauge a message's relevance and interest. It's therefore important to encourage your recipients to open and click in your messages. This will also affect your reputation, and consequently, the performance of future campaigns.

Moreover, with the implementation of Apple's Mail Privacy Policy, the opening data becomes unreliable. By encouraging your recipients to click, you'll have a more accurate view of the true interest in your messages (remember, Actito no longer counts openings made from iOS15 and higher).

Display Name

This is the sender of the message. The recipient must be able to easily identify this sender and it must not be misleading. If the recipient does not correctly identify the sender, they may not open the email or even complain.


Key Takeaways

Email deliverability, when understood, measured, and optimized carefully, ensures the efficient delivery of your messages to their destination and fosters the desired engagement from your recipients. However, reputation has now become the key to the success of email marketing campaigns. This reputation depends on the quality of the database, the engagement of recipients, and the relevance of the messages sent. Thus, beyond mere technical setup, the focus is on genuine engagement with the contacted audience. By investing in solid relationships with your audience, offering relevant content, and meeting the needs of recipients, you bolster your reputation and cultivate a loyal base of engaged subscribers, essential to your success.

Ultimately, by optimizing email deliverability and nurturing a solid reputation, you enhance your brand's credibility, retain your audience, and maximize the return on investment of your email marketing campaigns.

Beware, some rules are changing in 2024! Find out more in our article on the subject.

Thanks to Anne-Claire Fichten, Deliverability Team Manager at Actito, for her assistance in writing this article.

About the author


Isabelle Henry

Head of Inbound and Growth

Always on the lookout for new skills and always ready to launch new marketing projects at Actito, I rely on my personal experiences but also on everything that is happening in the digital world to continue to learn, educate and share with you through inspiring content. My little extras? Video editing and photography!

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