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Email Deliverability

How to improve email deliverability

Whether your email communications are for marketing, transactional or personal purposes, email deliverability is often one of our biggest bugbears when it comes to ‘doing business.’

8 minute read

In this piece, we explore how to improve your Sender Score, which in turn will increase email deliverability for your business. Implementing the below tactics will dramatically enhance this score and your IP’s reputation in weeks. However, you must maintain best practice to see long-lasting results.

Warm-up your IP

Internet or Broadcast Service Providers (ISPs) are constantly working to filter our spam, with roughly 1 in 6 emails ending up in our junk folders. This means that it’s imperative to build and maintain your IP’s reputation to reduce your email’s likelihood of getting lost.

One of the best ways to do this is through ‘warming up your IP’ by sending your marketing emails in batches. We recommend starting small at say 50 a day and then working your way up. You should also only send to valid emails, but we talk more about that later. This method builds trust and credibility with ISPs as more users start to open up and engage with your emails. It’s also a proven tactic in helping to increase the deliverability of your emails.

Consistency is key

Erratic, infrequent activity and blasts of email marketing can cause IP rejection and blacklisting. Creating a consistent schedule for your email that strikes the right balance is key to building trust with ISPs. We recommend sending your emails on the same day at the same time and no more than once a week – although this will depend heavily on your use of segmentation, the relevance of your content and your database engagement. We recommend using the same ‘sender’ for your emails instead of changing from company to person each time. Something like ‘Rich from Supersonic Playground’ is a nice way to make it personal while also being transparent to who the email is from.

If you are sending regular email blasts, we recommend giving your audience the ability to update their preferences or snooze your emails. This will help prevent opt-outs and spam complaints.

Create healthy lists

It’s easy to get swept up in email marketing and the results it can generate. However, it’s equally important to ensure you’re creating and maintaining valid, healthy email lists. There are several ways for you to do this:

Use a double opt-in

Double opt-in requires users to confirm they want to receive your emails after they’ve ticked the ‘send me marketing emails’ box on one of your forms. This method helps prevent spam addresses from entering your sending list, and it ensures the user wants to receive your emails. We know it might be tempting to use a pre-selected or required check box for your forms, but it can come across as forceful, and it can hurt your email deliverability as it encourages spam complaints. While it might take longer to build your list this way, you can rest assured that it’s a strong and engaged audience that will result in higher deliverability.

Simplify the opt-out process

Under GDPR, you have to give users the ability to unsubscribe to your emails. Still, it’s also good practice to ensure this process is as seamless as possible to build trust and credibility and prevent any lasting adverse effects. It’s also better for deliverability if users opt out instead of marking your emails as spam, so ensuring this process is smooth is vital. You could also use this as an opportunity to ask users why they’re unsubscribing to your emails. This will give you insight into what you could do better or whether their emails are just too chaotic for marketing.

Validate emails

Email hygiene is essential, and the best way to maintain this is by purging your list of hard bounces and old accounts. This process can dramatically improve the chances of your emails hitting inboxes, as low bounce rates and a healthy reputation are vital to email success.

Use segmentation

Segmenting your list can improve email open rates by 39%, and since high engagement is the best way to build trust with ISPs, it’s also the surest way to ensure your emails continue to get delivered. Segmentation will also help minimise the likelihood of your emails being marked as spam and the number of unsubscribes.

Test your spamminess

Emails that are seen as ‘spam’ or ‘unsolicited’ raise red flags for service providers and can result in your IP being blacklisted. If this does happen, there is a delisting process that can reverse this within 24 hours, but we recommend checking your IP reputation ahead of any email marketing activity.

Send Score is another free tool that will allow you to check your sender score. Realistically, you should be aiming for 80+ to ensure your emails are getting through ISP filters.

Testing your email campaigns themselves before you send them can also help improve deliverability rates by reducing the risk of getting marked as spam due to their code or content. Mail tester is a great and free way to do this, and all you have to do is send your test email to the address generated onscreen.

Authenticate your domain

Implement an SPF

A Sender Policy Framework (SPF) increases trustworthiness with email servers by allowing them to cross-reference the domain name against the associated IP address to ensure legitimacy. Not having an SPF in place can also cause your emails to get rejected.

SPF records use a DNS TXT record to determine hostnames and IP addresses that are authorised to send emails on behalf of a domain. This helps ISPs determine if a sender is legitimate or not. To set this up, you’ll need to contact your domain provider or host. You can also find out more about how to set up an SPF record here.

Setup a PTR record

PTR records are also known as reverse DNS records. Ensuring that your IP address and domain have matching reverse and forward DNS records can dramatically increase your sender score. We recommend speaking to your hosting company to see if this is already set up or something they can help you implement. You can find more information about setting up a PTR or reverse DNS record here.

DKIM and domain keys

Domain Keys Identified Mail (DKIM) prevents email spoofing by ensuring that messages aren’t altered in transit from sender to recipient by authenticating the sender with a public DKIM key listed in your domain’s DNS records. You can find out more about DKIM setup here.

Authenticate your ESP

If you’re using an Email Service Provider (ESP) such as Mailchimp, then you must ensure you’ve authenticated the ESP to send emails on your behalf. You can learn more about this here.

You might also use a service such as SendGrid to send your transactional emails (automated emails sent via your website), and again you can learn more about setting this up here.

Transactional emails and spam

Transactional emails specifically refer to the messages exchanged between your website and a user. These might include order confirmation emails, checkout abandonment emails or even emails confirming a successful download or form submission. The following tactics will help you ensure these emails do not negatively impact your email deliverability.

Install WAF

A Website Application Firewall (WAF) will help prevent your site from unwanted traffic by adding a layer of protection between your server and HTTP traffic from the internet. For example, you might choose to exclude traffic from countries that you don’t directly serve. You can also use a WAF to prevent blacklisted IPs from reaching your site and any potentially malicious traffic. By reducing the amount of suspicious traffic that lands on your site, you can help reduce your website’s likelihood of being spammed (thus preventing spam from being sent by your email server) and, therefore, any negative repercussions to your email deliverability. Learn more about WAF security here.


ReCAPTCHA can also prevent spam from attacking your forms by preventing bot and bulk attacks. Again, it’s important to protect your site from spam, which can negatively impact email deliverability if you do fall victim. Some examples have been listed below, but you can learn more about spam prevention and recapture here.

  • Honeypot – a basic contact form protection using an invisible field that a human wouldn’t complete (as they wouldn’t be able to see it), but a bot would, therefore filtering out submissions from bots.
  • CAPTCHA – uses graphics to show distorted characters and asks users to type what they see.
  • reCAPTCHA – similar to CAPTCHA but Google’s version, reCAPTCHA displays a checkbox or grid of images and asks users to select all those that show a particular item, i.e., traffic lights.
  • Human question or simple CAPTCHAs – a question only a human could answer, i.e., what’s 3 + 2.

Email deliverability can be a tricky subject to get your head around. Hopefully, this has helped you pull together a few tactics you can use to improve your emails’ performance. Don’t forget to contact your domain provider for more authentication information too.

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