EmailTooltester is supported by readers like yourself. We may earn a commission when you purchase through our links. Of course, this won't increase the cost for you.
You probably know that email deliverability and sender reputation are vital if you're sending out email newsletters and campaigns, but why is it important? And what can you do about it? In this post, I'm going to look at the importance of email deliverability and all the things you need to do to achieve a good deliverability rate.
There are many things you can do to improve email deliverability. Some of these are more time-consuming than others, but all of them will help in some way to increase your chance of reaching someone's inbox, instead of joining the other 162 billion emails in the spam folder.
In this article, we'll include information on the most essential practices, including:
- How to authenticate your email account;
- How to improve your sender reputation;
- How to improve your email content;
- How to increase email engagement
Sometimes, it seems like it would take too much time to do things the right way. Or that you don't have enough resources available to make it happen. But there are ways to increase email deliverability without having to spend a lot of extra time or money.
What is Email Deliverability?
Email deliverability is the ability of an email to successfully reach the intended recipient's inbox.
Successfully delivered emails are those that reach the main inbox. In the case of newsletters, this also includes e-mails that end up in the Promotions folder.
Undelivered emails are those that only reach the spam folder or are completely blocked (so that the recipient never sees them).
According to our email deliverability tests, we found that email deliverability averages 81%, meaning that 19% of all emails go missing or are caught by spam filters. And other deliverability data suggests that 1 in 7 marketing emails never reach the inbox!
If you’d prefer to learn by watching, follow our Email Deliverability Best Practices video:
Components of a Good Email Program
As we’ll explore in more detail, the key components for ensuring high deliverability include:
- Starting with the right infrastructure: This means choosing an ESP with reliable deliverability rates, but also making sure you’re sending from a reputable IP, and have technical aspects like authentication correctly set up.
- Good Data Practices: Ensuring clean and engaged email lists.
- Effective Design: Crafting emails that add value and engage subscribers, while also taking into account readability and accessibility.
Common Delivery Issues
Understanding common delivery issues can help you address them proactively:
- Throttling: When an ISP limits the amount of mail they accept from a sender.
- Spam/Bulking: When emails from a sender are consistently sent to the spam folder.
- Blocks: When an IP or domain is rejected by an ISP due to poor reputation or spammy content.
- Bounces: Emails that cannot be delivered. Soft bounces are temporary issues, while hard bounces indicate invalid addresses.
- Spam Complaints: If one of your subscribers marks your email as spam, an abuse report is submitted to their service provider, which can cause you to be penalized in future campaigns.
6 Email Deliverability Best Practices To Follow
To improve email deliverability, it is important to follow best practices for sending emails, such as using a reputable sending domain and IP address (and in some cases, considering a dedicated IP), avoiding spammy language and formatting, and obtaining consent from recipients before sending them emails.
Interestingly, our independent study on email politics found that political parties didn't always follow these best practices, resulting in higher volumes in the spam folder. Find out more here.
We’ve put together a list of the most important best practices you must follow if you want to land your emails in the recipient’s inbox.
1. Authentication
Email authentication is the process of verifying the identity of the sender of an email message. It is used to help protect against spam and phishing attacks, and to ensure that emails are delivered to the intended recipient.
There are several methods of email authentication, including:
SPF (Sender Policy Framework) defines the allowed mail servers for a given domain. When someone receives an email, their inbox server can check the SPF record to determine if the server that sent the email is authorized to do so. Example: I want to send newsletters for EmailTooltester.com via Brevo. For this to work, I have to enter Brevo’s mail server as “desired” in the SPF entry beforehand.
DKIM (DomainKeys Identified Mail) provides emails with a digital signature. The recipient's server can then check whether the email is genuine. In comparison to SPF, where only the IP address of the mail server is checked, the DKIM procedure tests the email itself. The digital signature, which is located in the email header, is checked.
DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a system that improves on SPF and DKIM. It lets you specify what should happen if either of the other two methods fail. It decides whether the email should be rejected or moved to the spam folder. There is also a “none” policy, which says that the email will be delivered normally, but the DMARC record will still collect data about failed authentication attempts.
By implementing SPF, DKIM and DMARC, plus other email authentication methods, organizations and individuals can help to protect their email communications and improve the deliverability of their messages.
How to Authenticate Your Email Account
It is important to note that the specific steps for authenticating your email account may vary slightly depending on the email service provider and domain registrar (e.g. Namecheap, GoDaddy, etc.) you are using. Consult your provider's documentation or customer support for specific instructions.
Check out our complete guide to email authentication for more information.
2. Sender Reputation
The sender reputation is a measure of the quality of a sender's email. It is used by mailbox providers like Gmail and Outlook to determine how likely it is that an email is spam or legitimate. Of course, the better the sender reputation, the more likely it is that your emails end up in the recipient’s inbox.
Sender reputation is based on a variety of factors, including the IP address and domain of the sender, the content of the emails, and the recipient's interactions with the emails (ideally it gets opened, in the worst case it gets flagged as spam). Mailbox providers use this information to calculate a sender's reputation score, which is used to determine how to handle emails from that sender.
Here are some tips for maintaining a good sender reputation:
- Use double opt-in for email list sign-ups: This ensures that only people who have actively requested to receive your emails are on your list. And remember: no one ever signed up for mass cold outreach, so please don't do it.
- Use a reputable email service provider (ESP): These providers have systems in place to help prevent spam and maintain a good reputation for their IP addresses. The top-rated ESPs you find on EmailTooltester are generally equipped to deliver your emails reliably if you follow the best practices of this article.
- Warm up your email account: Sending a large volume of emails from a new or inactive account all at once can trigger spam filters and result in a poor sender reputation and high spam score. Gradually increase the volume of emails sent from a new or inactive email account in order to establish a good sender reputation.
- Follow email best practices: This includes using a clear and accurate subject line, not using too many images or links, and including a clear and easy way for recipients to unsubscribe from your emails. (More on this below.)
- Monitor your email list health: Keep an eye on your bounce rate, complaint rate, and email delivery rate, and remove inactive or invalid email addresses from your list.
- Use authentication methods: These include SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) to help protect your sender reputation. (See above.)
- Pick your email sender address wisely: there is a case for and against using subdomains that we discuss in our separate article.
Also, consider using a dedicated IP address. Most platforms start you out on their shared network of IPs. If you are only a small-volume sender or are just starting out, this approach might be beneficial as it can help you build up a positive sender reputation more quickly (rather than starting from zero).
On the other hand, if that IP is not healthy, then you could experience issues getting delivery at certain ISPs. For example, Hotmail and other Microsoft domains usually put more emphasis on the IP reputation as opposed to your sending domain (which Gmail gives more importance to).
If you opt for a dedicated IP (which we’d only recommend if you’re a high-volume sender of 100k+ emails per month), you’ll be the only sender using it. So if you have good clean data, send consistently, and have high engagement rates, you shouldn’t have any problems. If not, however, you’ll soon experience issues with getting into the inbox or being blocked completely.
To learn more about whether or not a dedicated IP makes sense for you, check out our detailed guide.
By following these tips, you can help maintain a good sender score and ensure that your emails are delivered to your recipients' inboxes.
3. Email Content
Spam filters use algorithms to analyze the content of an email and determine whether it is likely to be spam or legitimate.
If an email contains content that is commonly associated with spam, such as excessive use of images, links, or certain keywords, it is more likely to be flagged as spam and delivered to the recipient's spam folder, or rejected entirely. On the other hand, if an email contains high-quality, relevant content that is likely to be of interest to the recipient, it is more likely to be delivered to the recipient's inbox.
Email subject lines
- Avoid spammy language: Avoid using words and phrases that are commonly associated with spam, such as “Free,” “Congratulations,” or “Earn money fast.”
- Keep it short: Subject lines should be concise and to the point. Aim for around 50 characters or fewer. Test your subject lines with our free email subject line tester.
- Personalize the subject line: Use the recipient's name or other personal information to make the subject line more relevant and engaging. Email personalization results in a higher open rate and click-through rate.
Email body
Don’t:
- Use ALL CAPS and lots of exclamation points!!!
- Use colorful and different-sized fonts
- Send emails with broken HTML code
- Include links to sketchy websites (also avoid link shorteners like bit.ly)
- Add an excessive amount of images
- Add an excessive amount of links
- Use spammy language
Do:
- Add an easy way for readers to unsubscribe
- Produce well-written, concise content
- Add a clear call to action (CTA)
- Personalize your email content (e.g. use the recipient’s name)
- Only send content your recipients want to receive
- Make sure your email is optimized for mobile
For example, here is an email we sent our subscribers communicating the results of our latest deliverability test, which uses the contact name tag. You’ll also see we included a clear CTA button and link to the unsubscribe form:
>>Check out our guide on how to create an email newsletter.
4. Email Engagement
Email engagement refers to the actions that recipients take with the emails they receive, such as opening, clicking on links, and responding to the email. These actions can help improve deliverability because they signal to email providers that the recipient is interested in receiving the email and that it is not spam.
Here are a few ways in which email engagement can help improve deliverability:
Higher open rates: When a high percentage of recipients open the emails they receive, it can indicate to email providers that the email is relevant and not spam. As a result, email providers may be more likely to deliver future emails to the recipient's inbox.
Lower unsubscribe rates: If a high percentage of recipients unsubscribe from an email list, it can be a red flag to email providers that the emails are not wanted. Keeping the unsubscribe rate low can help improve deliverability.
Lower complaint rates: If recipients mark emails as spam, it can hurt deliverability. Keeping the complaint rate low can help improve deliverability.
More clicks: When recipients click on links within an email, it can indicate to email providers that the email is relevant and not spam. This can help improve deliverability.
MailerLite Report
Interaction: If you receive regular responses to your emails or newsletters, this is a positive signal. Especially if you respond to them again. I have even come across email senders who actively ask their recipients to reply to autoresponder emails. Normally, the purpose of this is to improve the deliverability rate and thus also to get into the main inbox (and not only into the Promotions folder).
We encourage our readers to forward our newsletter
How to Get Higher User Engagement
So, how do you secure higher engagement from your recipients? Aside from personalizing your subject line and optimizing your email for mobile (which we’ve covered above), the following best practices will help you increase user engagement:
Ask questions: Simply ask your readers for specific feedback by directly replying to your email. This engagement can do wonders for your deliverability as a reply is a positive signal to mailbox providers. The same is true if your newsletter gets forwarded to friends and colleagues.
Segment your email subscribers: It’s important to segment your email subscribers so that you send them tailored, relevant content. If you get it right, this will really boost your open and click-through rate.
Send welcome emails: Welcome emails have an open rate of 86.03%, much higher than other email communications. It’s a simple thing to set up but can be very effective in getting you more engagement.
List hygiene: Actively remove inactive users from your mailing lists. There’s no point in emailing contacts that no longer wish to hear from you. This will increase your user engagement stats and keep your spam score low.
Use visually appealing design: Using eye-catching images and an attractive layout can help grab the recipient's attention and increase the likelihood that they will engage with the email. Need inspiration? Check out these newsletter examples for various industries.
Test and optimize: Use A/B testing to try out different subject lines, email formats, and calls to action to see what works best. Analyze the results and use them to optimize future emails.
5. Email Verification and Regular List Cleaning
Managing your email list isn't just about collecting new emails; it's also crucial to maintain list quality, especially if you are working with an older list. Here's how you can do it effectively:
a) Email Verification for Older Lists
If you’re uploading an older list, it's essential to verify its quality before sending any emails. Using a cleaning tool like ZeroBounce or Clearout helps remove bounced or inactive email addresses that could harm your sender reputation and deliverability. These tools flag addresses that are no longer in use or likely to cause bounces, helping you keep your deliverability intact from the start.
b) Regular List Cleaning for Ongoing Engagement
To maintain list health, establish a regular cleaning process to remove inactive subscribers who haven't interacted with your emails over a set timeframe. Depending on your email frequency, this could mean removing users after six months or up to a year of inactivity. Removing disengaged contacts helps improve your engagement metrics and shows inbox providers that your list is current and interested in receiving your emails, both of which contribute to better deliverability.
Here’s an example filter:
6. Email Deliverability Testing Tools
There’s a whole range of deliverability tools that we discuss in our separate article.
I am going to show you the two most important ones here:
- Google Postmaster Tools: it’s free and takes just seconds to set up if you have a Google account (don’t we all?). It will track your sender and domain reputation as well as authentication failures helping you investigate possible issues.
- DMARC Monitoring Tools: there are also good free ones available. These tools will also track authentication failures (not just for Gmail) and warn you of illegitimate senders using your sending domain.
In addition, you can use the following tools if you’re noticing concrete deliverability issues:
- Mail-Tester: a handy tool to quickly identify things like spammy content, blocklistings of your sender IP address, broken links, and other potential issues.
- Warmy (free) and Glockapps (paid) are inbox placement tools. By sending your newsletter to seed list addresses, you will see where they get delivered (inbox, promotions folder or spam). This can help you identify issues with specific mailbox providers. Keep in mind, though, that seed list tests generally show a lower deliverability rate than “real” emails.
How to Improve Email Deliverability? Conclusion
Email deliverability is an important email marketing KPI (key performance indicator) to be tracking. By following the best practices listed above, you can improve the chances that your emails will be delivered to the recipient's inbox and increase engagement with your recipients.
As you can see, there are a number of things you can do, and overlooking them would be a big email marketing mistake. If you don't follow these best practices, you will end up with poor deliverability rates and it will be difficult to rectify. Time really is of the essence, so make sure to start implementing these practices today!
And Finally, Test Your Knowledge With Our Quiz

If you have any questions, please drop them in the comments section below and we’ll do our best to answer them.
Do you want to collect more email subscribers? Check out our guide to email marketing lead generation.
Are you interested in making money via email marketing? Learn how to monetize your newsletter here.
We keep our content up to date
11 Feb 2025 - Small update
06 Nov 2024 - General update
20 Jun 2024 - General update
22 Aug 2023 - Added YouTube video
01 Mar 2023 - General update
Our Methodology
This article has been written and researched following our EmailTooltester methodology.
Our Methodology