Open Rate

The open rate is an email marketing metric that indicates the percentage of recipients who open an email in a campaign.

In other words, it measures how many people out of those who received your email actually opened it.

It is one of the key indicators for evaluating the performance of your email campaigns or newsletters, as it reflects the initial level of interest or attention your messages generate.

To calculate it, the following basic formula is used:

Divide the number of opened emails by the number of delivered emails, and multiply by 100 to express it as a percentage.

For example, if you sent 1,000 emails and 250 were opened, your open rate would be 25%.

You can use the following formula:

Open Rate (%) = (Opened Emails / Delivered Emails) × 100

It is important to note that “delivered emails” is not the same as sent emails; delivered refers to emails that successfully reached the recipient’s mail server (whether the inbox or spam folder), excluding those that “bounced” (bounces).

Thus, the open rate focuses only on messages that were successfully delivered.

The importance of the open rate in email marketing

The open rate is a key metric for several reasons.

First, it allows you to measure the effectiveness of the initial step in an email marketing campaign: getting the recipient to notice and open the email.

A good open rate indicates that the email has appealing elements (such as a catchy subject line, a recognized sender, etc.) that grab the subscriber’s attention enough to open the message.

Conversely, a low open rate can alert us to potential issues: perhaps the subject line is irrelevant, the recipient doesn’t recognize the sender, the message arrived at a bad time, or it went straight to the spam folder.

In terms of engagement, the open rate serves as an initial indicator of interest.

It is the first filter: if your subscribers don’t open your emails, it will be hard to get them to click on your content (CTR or click-through rate) or perform the desired action (purchase, sign-up, download, etc.).

Therefore, even though the final conversion doesn’t solely depend on opening the email, improving the open rate is essential to increase the chances of achieving your campaign goals.

Additionally, the open rate provides diagnostic information.

For instance, if certain campaigns or segments of your list have open rates well below average, it could be a sign of deliverability issues or irrelevant content.

Many email service providers (ESP) display this data in their reports because, when combined with other metrics, it helps paint a more complete picture of your email performance.

How is it calculated and what is considered a good rate?

As we have seen, calculating the open rate is simple.

However, determining whether an open rate is “good” or not requires context.

On average, the typical email open rate usually sits between 20% and 30%.

That is, for every 100 subscribers a campaign is sent to, typically between 20 and 30 end up opening the message.

However, this percentage varies greatly depending on several factors:

• The sector or industry
• The type of email (a promotional email is not the same as a transactional notice)
• The quality of the contact list
• And even the relationship you have with your subscribers

For example, highly anticipated newsletters or emails from trusted senders can achieve above-average open rates, while generic mass emails may fall below.

The type of audience also matters: in B2B (business-to-business) environments, open rates sometimes differ from B2C (business-to-consumer) environments.

Therefore, rather than comparing yourself to a standard percentage, it is better to establish your own benchmarks based on your previous campaigns and, if possible, comparisons with your industry averages.

For example, sectors like tourism or retail may have different averages than education or technology.

In short, a “good” open rate is relative: 40% could be excellent for a cold database, but perhaps insufficient for a hyper-segmented list of highly loyal customers.

The important thing is to analyze the trend (whether your open rates are going up or down over time) and optimize based on your own historical data and goals.

Factors influencing the open rate

Numerous factors can directly impact the open rate of your emails.

Below are the key elements to keep in mind:

Compelling email subject line (and appropriate preheader):

The subject line is probably the most decisive factor in encouraging users to open the email.

It should be catchy, clear, and relevant to the recipient.

A good subject line piques curiosity or indicates value (e.g., an offer, important news, useful content).

It is advisable to avoid:

• Overly long subject lines
• Confusing subjects or those containing spam words
• Unrealistic offers
• Excessive use of words like “free”
• Writing in ALL CAPS
• Excessive exclamation marks!!!, etc.)

Elements that could trigger anti-spam filters.

Along with the subject line, the preheader (the preview text that many email clients show next to the subject) should complement the message: a well-optimized preheader summarizes or adds engaging context, inviting the recipient to open the email.

Trusted sender name:

Recipients pay attention to who sends the email.

Using a recognizable and trusted sender name increases the chances of it being opened. It can be your company name or person + company (for example, “Maria from [YourBrand]”).

Avoid using generic addresses like “no-reply@” or similar ones that come across as impersonal.

Sender reputation also plays a role: if your previous emails have provided value, users will be more inclined to open future ones.

On the other hand, if your domain or IP is on a blocklist or your previous emails were annoying, trust decreases and open rates drop.

Contact list segmentation:

Segmentation in email marketing involves dividing your subscriber base into more homogeneous groups based on characteristics or behaviors (by interest, location, sales funnel stage, active customers vs. new leads, etc.).

Sending each campaign to the right segment improves the message’s relevance to the recipient, which typically increases the open rate.

For instance, a product update email sent only to those who have shown interest in that type of product will have higher open rates than if you blast it indiscriminately to your entire list.

Segmentation ensures that each subscriber receives content that matters to them, reducing the risk of them ignoring or deleting the email without opening it.

Content personalization:

Related to segmentation, personalization in email marketing also plays an important role.

Adding personal touches like the recipient’s name in the subject line or email greeting, or tailoring the content based on user data, can increase affinity and motivate them to open it.

Emails that seem generic or irrelevant to the user are less likely to be opened than those where the subscriber feels the message was crafted “just for them.”

For example, receiving an email that starts with “Hi John, we have a special offer for you” is not the same as one that says “Hello customer, generic offer for everyone.”

Personalization shows that you know your audience and is usually reflected in better open rates.

Best sending frequency:

Understanding the best time to send your emails can greatly influence open rates.

Sending an email at 3 AM will likely not be effective if your target audience isn’t checking their inbox at that time.

Studying the time slots and days of the week when your subscribers are most receptive (for example, some studies suggest mid-morning or post-lunch on weekdays are usually good times, but every audience is different) will help you to schedule campaigns for when your subscribers are most likely to be online.

Likewise, send frequency matters: if you bombard your subscribers with unexpected daily emails, you could cause email fatigue, leading them to ignore you or unsubscribe.

Conversely, if you are too infrequent, they might forget who you are.

Find a frequency balance that maintains interest without overwhelming them.

An occasional win-back mailing campaign or a well-planned weekly newsletter usually works better than random email blasts.

Sender reputation and deliverability:

This technical factor is critically underlying: even with the best subject line and segmentation, if your emails don’t reach the inbox, they will hardly be opened.

Deliverability refers to the ability of your emails to reach the inbox instead of landing in spam or bouncing.

To achieve this, you must protect your sender reputation (keeping spam complaints and bounce rates low) and adhere to technical best practices.

For example, setting up email authentication on your domain (SPF, DKIM, DMARC), using a reliable sending infrastructure, and avoiding content or patterns that anti-spam filters penalize.

If your domain or IP has been flagged for sending spam in the past, your emails could end up in the junk folder, causing your open rate to plummet.

That is why maintaining good list hygiene (removing or trying to re-engage inactive contacts, not emailing contacts who haven’t opted in), and sending quality content to audiences who actually requested it, will help both deliverability and open rates.

Best practices to improve your open rate

If your current open rate isn’t what you’d like or has been declining, it’s time to take corrective action.

Here are some best practices and tips to improve this metric:

Use double opt-in and quality subscribers:

Make sure your contacts actually want to receive your emails.

Implementing a double opt-in process (where the new subscriber confirms their subscription from their inbox) ensures that your list is made up of genuinely interested people.

This usually translates into better open rates, as you have more engaged subscribers.

Avoid buying email lists entirely or adding contacts without permission.

Regularly clean your contact list:

Periodically review your database to identify inactive subscribers (those who haven’t opened or engaged in months).

Keeping ghost contacts negatively impacts your metrics, including your open rate, and can harm your deliverability.

A recommended practice is sending re-engagement campaigns to those who have been inactive for a while: for example, an email asking if they are still interested or offering to update their preferences.

For those who don’t respond or show any activity, it’s best to unsubscribe them from the list.

Scrubbing your list by removing inactive emails will leave you with a healthier and genuinely interested audience, naturally boosting the open rate percentage for future campaigns.

Additionally, by reducing unnecessary campaignss, you will improve your reputation and even save costs on platforms that charge by number of used contacts.

Optimize subject lines (run tests):

Since the subject line is so critical, dedicating effort to optimizing it pays dividends.

Test different subject line approaches to see what resonates best with your audience.

An effective strategy is to run A/B tests: send two subject variants (for example, one emphasizing a discount and the other highlighting a solution to a problem) to a small sample of your list and measure which one gets the higher open rate.

Then send the winning version to the rest of the list.

A/B testing allows you to base your decisions on data rather than assumptions.

Remember that there is no universal “perfect subject line.”

And also note that with Mailrelay, you can generate subject lines using AI, which can be very handy for brainstorming ideas.

Provide valuable content and deliver on your promises:

In the long run, the best way to ensure good open rates is to earn the trust and interest of your audience.

If your email campaigns consistently provide value—whether it’s useful information, relevant offers, interesting news, or entertaining content—your subscribers will look forward to your messages and gladly open them.

Conversely, if your emails disappoint (too much self-promotion with no utility, or the subject promised something the content didn’t deliver), readers will lose interest.

Therefore, know your audience and send emails that you yourself would want to open if you were in their shoes.

Maintain consistency in both frequency and content type: if a user signed up expecting a monthly newsletter with tips, don’t let them down by sending daily emails full of pure advertising.

Meeting expectations builds a relationship with the subscriber and improves open rates over time.

In conclusion, the open rate remains a valuable indicator for understanding the initial performance of your emails and the health of your subscriber list.