What Is Email Deliverability? 6 Ways to Improve Email Deliverability

Making your campaigns reach your audiences’ inboxes is very important in email marketing because inboxed emails get customers’ primary attention. It’s also one factor that affects your return on investment (ROI).

If your emails don’t arrive in your customers’ inboxes, they will never know your latest product promotions, how to make a purchase, and the latest updates in your business. Simple Mail Transfer Protocol or SMTP relay is one of the services you should use to ensure your emails don’t end up in your customers’ spam folders.

In this article, we’ll let you know what exactly is Email Deliverability and the best practices to improve Email Deliverability and make email campaigns more successful.

What Is Email Deliverability?

Email deliverability is the measure of how likely your email campaigns are going to reach your subscribers’ inboxes. For example, if 95% of your campaigns arrive in your customers’ inboxes, that is considered a high deliverability rate.

But if 80% of your email campaigns are rejected, blocked, flagged, or sent to the spam box by the internet and email service providers (ISPs and ESPs), that means you have poor deliverability rates and unsuccessful email marketing campaigns.

Best Practices to Improve Email Deliverability

There are various ways to increase the rates of your email campaigns reaching your subscribers’ inboxes. Here are a few of them.

1. Use SMTP relays

Ordinary email accounts for businesses such as a Gmail account have email sending limits. If you intend to send 1000 emails per day to customers but have a 500 sending cap, the other 500 of your campaigns will not reach your recipients because they will be blocked automatically.

SMTP relay services usually have a 10,000 to unlimited outbound email cap per day. This means you can send as many emails as you want to customers, which increases your deliverability rates.

Another perk of SMTP relay is that the relay servers your emails are sent from are trusted by ISPs and ESPs. This means your email campaigns have the clearance to reach customers’ inboxes for marketing purposes.

2. Write non-spammy subject lines

ISPs have filtering systems that detect spammy words and phrases. Examples of these spammy words and phrases are sales words like “Cheap,” “Free,” and “Act now!”

It’s best to avoid using one-word subject lines, all-caps, and exclamation points as well. Another common mistake that you should look out for is spelling errors, for they can trigger spam checkers.

3. Follow a consistent sending schedule

Both ISPs and ESPs monitor your sending patterns and record that data to distinguish yourself as a legitimate email marketer against spammers. If you do not follow a consistent campaign sending schedule, you might be flagged for suspicious activity.

For example, send 5,000 campaigns on Tuesday and Thursdays while sending 2,500 for the other week’s days. Send them on scheduled hours. It’s also best that you make your campaign sending automatic for subscribers in different time zones.

4. Use double opt-in

There are a lot of email bots that infiltrate websites to join mailing lists. Some of these bots contain spam traps. Others add up to disengagement rates in your email campaigns. Disengagement rates can cause ISPs and ESPs to flag your email, domain, and IP address as a sender.

Using double opt-in authentication in your mailing list subscription system, you’ll filter out email bots and spam traps.

5. Clean up your list regularly

Sometimes disengagement rates are caused by customers who have stopped opening your emails. If you have customers on your mailing list that have gone inactive for a long time, remove them.

But don’t just remove them immediately from your mailing list when they didn’t read your campaign on two or five occasions. If their inactivity just started a few weeks ago, find a way to spark their interest in your business again by re-engaging them first.

Determine when was the last time these inactive subscribers opened one of your campaigns first. If the last time was 3 to 6 months and they never responded to your re-engagement strategies, that is a ground for removal because their stay will ruin your email marketing performance

6. Provide a preference center and segment users based on their answers

Preference centers are pages in your website or app that give your new subscribers the option to choose what type of content to receive from you and when to receive them. By providing your subscribers’ control, you’ll gain insights into making emails that spark interest.

Your audience will also be happy in opening your campaigns because they get to read your campaigns during hours they’re free. This, in turn, drives better engagement rates. ISPs will then notice these high engagement rates and give you the right sender’s reputation for high email deliverability.


ISPs and ESPs have various systems to determine whether your email campaigns are worthy of being sent to your recipients’ inbox. So follow the email deliverability boosting strategies in this list.

Don’t send emails to those who are no longer interested in your campaigns because they reduce your engagement rates. Give your subscribers more control so that you’ll send your campaigns at their preferred time.

Filter out fake emails and bots using double opt-in authentication. Don’t write sales and pushy subject lines to avoid your campaigns from being labeled as spam.

Use SMTP relay services to send campaigns from a trusted server. Also, follow a consistent campaign sending schedule so that ISPs can recognize your email sending behavior. We hope this guide helps! 

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