Deliverability in Email Marketing

Deliverability is a crucial term in email marketing, as it determines how many of your bulk emails actually reach recipients’ inboxes.

In other words, good deliverability ensures that your subscribers receive your messages and that your email marketing campaign doesn’t get lost in the shuffle because of spam or email filters.

Next, we’ll explain what deliverability is, how this concept works in bulk email sending and how to improve it to boost the success of your email marketing campaigns.

What is email marketing deliverability?

Deliverability in email marketing refers to the ability of your emails to reach your subscribers’ inboxes, rather than ending up in the spam folder or other secondary tabs.

This metric measures what percentage of emails sent are actually delivered successfully to the recipients.

Simply put, if you send 100 emails and 90 reach the users’ main inbox, we could say you have a 90% deliverability rate.

The standard formula to calculate this percentage is:

deliverability rate = (emails delivered / emails sent) × 100

It is important not to confuse deliverability with the “open rate” or the “click-through rate“.

Deliverability only measures whether the email is delivered (whether the message reaches the inbox), without taking into account whether the user then opens it or interacts with it.

Now that we have clarified what deliverability means, let’s see why achieving a high rate for your email campaigns is so important.

Why is deliverability important?

Deliverability is vital because an email marketing campaign is useless if your emails don’t reach the recipients.

No matter how well-designed your newsletters are or how attractive your offers are, if they end up in the spam folder or aren’t delivered, your efforts won’t yield results.

This translates into lost sales opportunities and a wasted investment of time and resources.

In addition, poor deliverability can damage your brand’s reputation.

When subscribers provide their email address, they are placing their trust in your company.

If your emails fail to reach their inbox, that trust is compromised.

As a result, poor deliverability affects your business’s credibility and even your revenue, since fewer emails being opened means fewer potential conversions.

In short, ensuring good deliverability is essential to the success of any email marketing strategy: it guarantees that the message reaches its audience and maximizes the return on investment of your campaigns.

How does email deliverability work?

Email deliverability works by taking multiple technical and behavioral factors into account.

Several factors come into play with every email campaign (your sender domain, the email platform, email providers’ filters, and the recipients themselves) that will determine whether a message reaches the inbox or is filtered out.

Essentially, deliverability is the result of a combination of key elements, including:

3 Sender reputation:

The reputation of your sending domain and IP heavily influences deliverability.

If you’ve consistently sent high-quality emails with low spam rates, email providers (such as Gmail, Outlook, Yahoo, etc.) will trust your messages more.

On the other hand, if your domain or IP address is blacklisted or has generated a lot of spam complaints, your emails will have trouble reaching their destination.

· Quality of the contact list:

The hygiene of your database is another crucial factor.

Sending emails to invalid, outdated, or inactive addresses harms deliverability because it increases the bounce rate and may signal to providers that you’re not managing your email campaigns properly.

Maintaining a clean list (without non-existent or inactive contacts) ensures your messages are only sent to real and interested recipients.

· Subscriber interaction:

The behavior of your readers also affects deliverability.

If users regularly open, read, and click on your emails, email providers will interpret your messages as relevant and desired, improving your chances of reaching the primary inbox.

On the other hand, if many subscribers mark your emails as spam, delete them without reading them, or never interact with them, spam filters will interpret your content as unwanted and may move it out of the inbox in future mailings.

· Email content and anti-spam filters:

What and how you communicate in your emails influences their delivery.

An overloaded design, containing only images or using excessive spam trigger words (like “free”, “offer”, “urgent”) can trigger anti-spam filters.

Similarly, poor HTML formatting or suspicious links are a red flag for filters.

Email services analyze elements such as the subject line, message body, and formatting for signs of spam or phishing.

If the content seems suspicious or inappropriate, the email will likely end up in the spam folder.

· Authentication and technical setup:

Technical aspects such as configuring SPF, DKIM, and DMARC —email authentication protocols—have a direct impact on deliverability.

These settings tell the recipient’s provider that your emails are actually coming from you (from your legitimate domain) and not from an imposter.

For example, a correctly configured SPF indicates which servers are authorized to send on behalf of your domain, and DKIM adds a digital signature to your messages.

If you don’t have these measures in place, many servers might reject your emails or mark them as suspicious.

Having an email marketing platform that properly manages these authentications significantly improves your delivery rates.

In summary, deliverability works as a delicate balance between reputation, contact list quality, the content you send, and the technology backing your emails.

Understanding these factors will help you identify what might be failing if your emails aren’t arriving and, above all, how to fix it.

How to calculate the deliverability rate

The most useful formula to estimate it is this: emails that reach the inbox ÷ emails delivered × 100.

The problem lies in the numerator. Email marketing tools know about acceptances and bounces, but they don’t always receive the exact location of each message.

That is why the deliverability rate is usually estimated with placement tests and complementary signals. It is worth reviewing opens, clicks, bounces, complaints and errors by provider.

A drop in opens does not prove a deliverability problem by itself. It may be due to a weak subject line, an offer that isn’t very relevant or privacy changes.

Look for several signals pointing in the same direction. Analyzing them together gives a much more reliable picture.

What counts as good email deliverability

There is no universal percentage that guarantees results. The figure changes depending on the industry, the country, the email provider and the quality of the audience.

As a guideline, a delivery rate below 95% deserves an immediate review. For inbox placement, the closer you get to 100%, the better.

Compare each campaign with your own history. Also separate the results for Gmail, Outlook, Yahoo and corporate domains.

An overall average can hide a major block. Your emails may reach Gmail well but suffer rejections at Outlook.

If you are looking for local context, check out our analysis of email marketing deliverability in Spain.

How to know if you have a deliverability problem

A sudden drop needs context. Before changing everything, identify when it started and what changed on that date.

Error codes provide more precise clues than a general impression. A rejection due to authentication requires a different fix than a nonexistent mailbox.

Google Postmaster Tools also lets you monitor reputation, authentication, errors and spam for Gmail. Compare that data with the reports from your platform.

How to improve deliverability in your email marketing campaigns?

Achieving good deliverability is not a matter of luck, but of consistently applying a series of best practices.

If you are wondering how you can increase that inbox delivery rate, below we review several key tips.

By following these recommendations, your bulk emails will be much more likely to end up in your subscribers’ inboxes:

· Use a reliable and high-quality email marketing platform

The first step to improving your deliverability is ensuring you send your emails through a reliable email marketing tool.

Professional platforms (such as Mailrelay, for example) have optimized infrastructure, servers with a good reputation and strict anti-spam policies.

This means that by using a reputable service, your messages start with an advantage in being accepted by email providers.

Additionally, these platforms usually handle complex technical aspects – such as SPF/DKIM authentication or blacklist monitoring – so you don’t have to worry about them.

In short, rely on a good bulk email service that ensures the deliverability of your campaigns from a technical standpoint.

· Implement double opt-in on your subscription forms

An effective way to protect your deliverability is to build a list of contacts who are genuinely interested in your content.

To achieve this, use double opt-in for subscriptions: this method requires the user to confirm their email by clicking a confirmation link sent to their inbox after registering.

Why does this help?

Because it ensures that every email address in your database belongs to an active person willing to receive your messages.

With double opt-in, you avoid fake or incorrect contacts and guarantee higher-quality subscribers, reducing future spam complaints and improving the performance of your campaigns.

· Don’t buy email lists or send emails without permission

It may sound tempting to try to quickly grow your list by purchasing a database or adding contacts who haven’t given their consent, but this is a bad practice that seriously harms deliverability.

Contacts who haven’t subscribed to your emails are very likely to ignore them, delete them, or mark them as spam.

The latter, in particular, is devastating to your reputation as a sender.

Furthermore, in many countries, sending unsolicited emails violates data protection regulations.

Therefore, build your list organically: gather subscribers through forms on your website, events, social media, or other channels where they voluntarily express their interest.

Quality is better than quantity when it comes to email marketing.

· Keep your subscriber list clean and updated

Email list hygiene deserves constant attention.

Over time, it is normal for certain contacts to stop interacting or for some email addresses to cease to exist (due to job changes, new providers, etc.).

That is why it is important to regularly clean up your database.

Remove or try to reactivate subscribers who have been inactive for a long time, and be sure to remove email addresses that generate hard bounces because they no longer exist.

Maintaining a clean list reduces the proportion of emails that never arrive (due to full or non-existent inboxes) and shows ISPs that your sending practices are responsible.

As a result, your deliverability will improve because you’ll be sending emails to an audience that is truly active and interested.

· Take care of your email content and formatting

The content you send is your cover letter to both spam filters and your subscribers.

To optimize deliverability, send high-quality, relevant content to your audience.

Avoid overusing words considered spam or flashy symbols in the subject line (like ALL CAPS or exclamation marks such as “BUY NOW!!”), as they can trigger alerts.

Likewise, balance text and images: an email that is a single large image with hardly any text may look suspicious to filters.

Ensure your message is well-formatted, with clean HTML if you use it, and include descriptive alt text for your images.

A clean, professional, and useful email is more likely to pass anti-spam filters and also capture the positive attention of your subscribers (which, in turn, improves future deliverability).

· Segment your campaigns and personalize the message

Not all your subscribers are the same, so sending everyone the same message can result in a lack of interest from many.

By segmenting your list into more specific groups (for example, by interests, geographic location, stage in the buying cycle, etc.), you can personalize the content and send truly relevant information to each segment.

Why does this improve deliverability?

Because recipients get emails they are interested in, making it more likely they will open and interact with them.

Higher engagement (opens, clicks, replies) signals to Gmail, Yahoo!, and other providers that your emails are well-received, reinforcing your reputation as a legitimate sender.

As a result, segmentation and personalization are a winning strategy: they improve the user experience and boost your delivery metrics.

· Send with the right frequency and consistency

Consistency in your sending frequency also plays a role in deliverability.

Try not to go from 0 to 100 abruptly; that is, avoid sending very few emails for weeks and suddenly sending a massive volume all at once, as those unusual spikes can trigger spam alerts.

It is advisable to maintain a regular sending frequency (for instance, a weekly or monthly newsletter, depending on your strategy) so that both your subscribers and email servers “expect” your messages.

If you need to increase your sending volume (for example, during a special promotion), do so gradually or in stages.

This process, known as warming up (IP or domain warm-up), helps email providers see your growing sending volume as normal.

In short, send emails on a regular and consistent basis, because extreme irregularity can harm your reputation and, as a result, your deliverability.

· Configure authentication: SPF, DKIM (and DMARC)

Lastly, don’t neglect the technical aspects backing your sends.

Configuring SPF and DKIM records on your domain is essential to improve the deliverability of your emails.

These protocols serve to validate that you are who you claim to be when sending an email: SPF specifies which servers are authorized to send emails from your domain, while DKIM adds a digital signature to each message to confirm it hasn’t been altered and comes from a reliable source.

Implementing DMARC as well can give you an extra layer of protection, instructing receivers on what to do if a message fails SPF/DKIM checks (for example, rejecting it or sending it to spam).

By having these authentications correctly configured, your emails will build more trust in the eyes of Gmail, Outlook, and others.

Many email marketing services guide you through this process.

Taking the time to activate SPF, DKIM, and DMARC directly results in a higher delivery rate.

What to do if deliverability suddenly drops

First, pause the least important sends. Continuing to push can prolong the damage, especially if complaints or bounces are rising.

Then, review the SMTP codes, authentication and recent changes. Also check whether your domain or IP appears on an email blacklist.

Send your next campaigns to the most active segment. Reduce the volume and get back to a steady cadence while you watch the response by provider.

Don’t delete your whole list without analyzing it. Separate active, inactive, bounced and never-engaged contacts. Each group needs different treatment.

Recovery rarely happens within hours. Filters need to receive new, consistent signals before updating their assessment.

What is the best email marketing tool to improve deliverability?

Choosing the right platform can make a huge difference in the deliverability of your campaigns.

The best email marketing tool will be the one that offers a solid infrastructure, strict anti-spam policies, and support to implement sending best practices.

Mailrelay, for example, stands out as a platform designed to maximize deliverability: it offers high-reputation servers, the ability to easily configure SPF/DKIM, and an expert support team that is there to assist you at all times.

In addition, Mailrelay offers you the largest free account on the market (up to 80,000 emails a month to 20,000 subscribers) and human technical support on all accounts, even the free one.

These advantages allow you to improve your deliverability with zero initial investment, as you can send mass campaigns, monitor your results, and clean your lists with professional help.

Ultimately, if you want to make sure your emails reach the inbox, it’s crucial to rely on a trustworthy email marketing tool like Mailrelay, which combines excellent technical features with expert support.

This way, you can focus on creating great content while the platform ensures your messages reach your customers!

Frequently asked questions about deliverability

These answers address the questions that usually come up before sending a campaign or during a delivery problem.

Why do my emails land in spam?

The most common causes are incomplete authentication, poor reputation, complaints, lack of engagement or old lists. Irregular volume, links and content also play a part. Review the delivery codes and segment the data by provider before drawing conclusions.

Are deliverability and delivery rate the same thing?

No. The delivery rate measures the messages accepted by the receiving server. Deliverability estimates how many of them reach the inbox. An accepted email can end up in spam, so both metrics should be analyzed together.

What is email delivery?

It’s another name for the email delivery process: the message leaves the server, the recipient’s provider accepts it and it reaches their mailbox. Deliverability goes one step further, because it measures whether that email reaches the inbox rather than spam.

Do SPF, DKIM and DMARC guarantee reaching the inbox?

They don’t offer a guarantee. These protocols authenticate the origin and help protect your domain. Providers also weigh reputation, complaints, volume and recipient engagement.

What bounce rate is acceptable?

The lower, the better. A rate above 2% usually justifies a review of the list and its origin. Hard bounces should stop receiving emails, because they correspond to invalid or nonexistent addresses.

Does a dedicated IP always improve deliverability?

Not always. A dedicated IP offers more control, but it also requires enough volume and constant management. With low traffic, quality shared infrastructure can be more stable.

Should I remove all inactive subscribers?

First define what “inactive” means for your purchase cycle. Then try a reactivation campaign. If there is no response, excluding those contacts usually protects costs and reputation.

How long does it take for a domain’s reputation to recover?

It depends on the severity and the history. An improvement can take days or several weeks. Fix the cause, reduce the volume and send consistently to active contacts.

Does switching platforms fix poor deliverability?

Only when the previous infrastructure was part of the problem. If you keep a poor list, high complaints or a badly authenticated domain, you will just carry the problem over. Audit your data, setup and strategy first.

Do words like “free” make an email go to spam?

An isolated word rarely decides the fate of a message. Filters evaluate many signals. Avoid misleading promises and combine clear content with good reputation, permission and authentication.

How can I test deliverability before sending?

Check SPF, DKIM and DMARC, review the spam report and send tests to several providers. For sensitive campaigns, use an inbox placement test. Then validate the real result with reports, SMTP codes and reputation data.