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  • Writer's pictureolena severyn

What is email deliverability, why it matters and how to improve it.

What is email deliverability?

Email deliverability is the ability to deliver emails to subscribers’ inboxes. An email deliverability rate can be lower when an email bounces or gets automatically filtered into a spam folder. Deliverability is also related to inbox placement – whether an email appears in the primary inbox, the promotions tab or social tab, or the spam folder. A failure to reach customers reduces the performance of a marketing email, which is one reason that deliverability is extremely important to every business. Email deliverability is often measured as a percentage of emails accepted by the internet service provider.

Factors such as sender reputation, authentication, and being blacklisted are all common reasons for low email deliverability. Being very clear about the content you send, and to who you send it to, is very important to maintain a high rate.

What is a bounced email?

If the email failed to reach the subscriber is called a bounced email. There is a soft and hard types of bounced email. Soft bounce usually happens due to the reasons that can be resolved - such as full inbox. A hard bounce is a permanent type of bounce that means there is something wrong with the email address you’re trying to reach. A single hard bounce is a sign that you should remove that email address and won’t affect you too much, but if you continuously get these hard bounces, it will signal to your ISP that you’re not keeping up with proper list hygiene and will begin to hurt your reputation and email deliverability.

Things that improve email deliverability:

1. Have clear unsubscribe link and honour your unsubscribes.

It is the law that you should stop sending promotional emails to the customers who choose to opt-out from your list within 10 days. When someone unsubscribes, Klaviyo will suppress them to ensure that they no longer receive emails from you.

2. Include a physical mailing address in every email.

3. Use clear "From," "To," and "Reply to" language that accurately reflects who you are.

4. Include alt text for all imagery.

5. Stay consistent with campaign frequency.

The more consistent your sending schedule is, the better your deliverability would be. The ISP love to consistency - either its 1 or 5 emails a week - it will get used to it. So increase your frequency incrementally and stick with it. If there is a multiple day promotion coming, build up to those few days of emails by teaser emails every few days leading up to the promotion.

6. Clean your email list

Keeping your list clean will improve your deliverability. You should create a habit of removing inactive subscribers on a monthly basis - put some effort into reengaging them, if that doesn't work - suppress them so they don't hurt your sender reputation and deliverability.

7. Exclude spam traps.

Spam traps are fake email addresses that live on the web for the purpose of finding people who may be illegitimately acquiring contacts.Sending to spam traps or actual humans who do not engage (open/click) with your emails will cause deliverability issues. Here is some details about how to identify Spam Traps accounts.

Since there are things that spam trap accounts cannot do, it makes it easy to identify them and exclude from all your email communications.

8. Create engaging content

Your content must be exciting, interesting, encouraging people to engage. If they don't - your click rates will go down and that is not going to be good for your deliverability. Subject lines that stand out, attractive design that is optimized for mobile, clear CTA button, and never-ending A/B testing will help you hit customer's inboxes. Things like header image/no header image, copy length, CTA button placement, subject lines tone, colors - all must be tested, always.

Things that destroy email deliverability:

1. Buying or transferring email lists.

This is a sure way to not only get sent into the spam, but even get your account blocked. Good luck trying to unblock it later on!

2. Using too many gifs, emojis, exclamation marks, all caps in email or subject lines

You should avoid sounding too salesy by removing words from your subject line like:


Click here

Offer expires

Limited Time

Cash or money


Free or Free Gift

Instant Access

3. Using deceptive subject lines.

Your subject lines must reflect the content of the email.

4. Emailing people who bounced repeatedly

Bounce rates are one of the key factors internet service providers (ISPs) use to determine an email sender's reputation, so having too many hard bounces can cause them to stop allowing your emails in folks' inboxes.

One way to deal with this is to create a segment for your exclusions list that will automatically filter out those who have bounced in the last 7 days

5. Sending emails to unengaged subscribers

Email providers always make sure that the content their customers receive is a relevant one. Which means that if your subscribers are not engaging with your emails, the email provider will notice and your chances to end up in promotions tab or even spam become higher.

Repeatedly emailing unengaged recipients will cause ISPs (e.g., Hotmail, Gmail, Outlook, etc.) to evaluate whether each recipient wants to receive emails from your domain. If there is a continuous period of time, usually around 60 days, when a recipient receives multiple emails from you but does not engage, ISPs will take that as a sign that they do not want to receive your emails and will likely route them to the spam folder or block the delivery outright.

To avoid this, use segmentation. The very first segment you need to create is your engaged segment - never send to your entire list unless it is happening once quarterly as a part of your strategy.

Here is the definition of a 90 days engaged segment.

Start with 30 days engaged, take it up to 60 or 90 only when your benchmarks are in the healthy range. It is not better to send to more people - if your benchmarks are below normal, the chances that your engaged subscribers will see your emails diminish.

Benchmarks for sending performance

6. Low open rates

The more your emails get unopened, the lower your sender reputation will be. So make sure to say above that 20% mark. If your open rates are currently lower, go ahead and shrink your recipient's segment. If your metrics are really low (below 10%), it can also mean that you have earned bad sender reputation and your emails are going to spam - so account rewarming might be needed.

7. Not warming your account when you first starting with Klaviyo.

Warming involves building sending reputation, and gradually increasing email volume that is sent from a new domain or sending IP. If you are just starting with Klaviyo, take advantage of their new feature - guided warming.

If you've been with Klaviyo for a while and you know that your emails are often go to spam, you can rewarm your account and build trust again - follow standard guided warming process.

Note: The process will vary depending on whether you are sending from dedicated IP or shared IP. Setting up a new dedicated IP is an entirely different process than ramping a shared IP, as dedicated IP’s need to be fully warmed while shared IP’s are more focused on ramping your send volume.

8. Sending same messaging to one list.

Segmentation is the key to creating content that your subscribers will engage with - and high engagement means good deliverability! At different stages of the customer journey your subscribers want to hear different content from you. For example your brand enthusiasts want early access to your new collections, while nearly theres might need a discount.

Create segments based on purchase history (recent purchasers, 1st time buyers, active on site, etc), on collections of interest, on level of engagement (potentials, brand enthusiasts, lapsed purchasers, high rollers, etc), average order value, loyalty program tiers, and so many more!

Final Thoughts

You can design the most beautiful email with the most engaging content, but it won't matter unless that email makes it to the subscriber's inbox. You need great email marketing strategy to land in the subscriber's inbox, that's why it is so important to follow the best deliverability practices outlined in this article and watch your metrics.

To sum up the main points:

  1. Follow the best email practices by: - including unsubscribe link and honouring unsubscribes; - including physical address of your business; - using clear "From" and "Reply to" email addresses -include Alt text for all imagery

  2. Clean your list regularly by suppressing inactive subscribers, spam traps, and bounced emails.

  3. Make sure your metrics are within a healthy range.

  4. Stay consistent with campaign frequency.

  5. Warm your account.

  6. Segment your audience.

Good luck!

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