How to improve email deliverability

Last Updated Feb 08, 2021
Emma Jagger

Engineer, maker, Google alumna, CMU grad

This article will discuss possible improvements to your email delivery system to increase your email delivery rate and your email campaigns' success.

Improvements in the registration process of your mailing lists.

  • Use a CAPTCHA system to ensure that only humans subscribe to your mailing lists and protect you from bots. Google provides an excellent CAPTCHA service.
  • Have new subscribers confirm that the email address belongs to them by sending a confirmation link to their email inbox before validating their account, and avoid bot and fraudulent subscriptions.
  • Use a real-time API to check email addresses at the time of registration to protect yourself against non-existent addresses, but especially against disposable email services. Abstract provides a free and robust API for this.

Configure your domain name correctly to improve email deliverability

  • Configure SPF authentication via a TXT record of your domain to specify which servers can send emails for your domain. Based on the whitelist principle, this will protect you from unauthorized emails sent with your domain name.
  • Configure DKIM authentication, also via a TXT record of your domain, to electronically sign with an asymmetric key pair all emails sent from your domain to protect you against email spoofing.
  • Configure the DMARC record, which allows you to publish your policy in terms of spam protection, but more importantly, to specify how other servers can forward authentication errors to URIs of your choice so that you stay informed of any attack on your email system.
  • Configure PRT records, also known as reverse DNS lookup records, to allow spam filters to authenticate your email servers efficiently and reduce the filtering rate.

Use a trusted and recognized infrastructure

  • Use recognized and trusted DNS providers and hosting services to increase the trust of mail servers globally. Many recognized DNS service providers exist on the internet, such as OpenDNS, Cloudflare, Google Public DNS, and much more.
  • Use reputable and trusted CDN providers for any enclosed content, such as images or videos, to reduce spam filtering risk by both servers and clients. For example, Cloudflare, Fastly, CloudFront, etc...

Gradually increase your campaign, sending volumes if you're experiencing deliverability problems

Don't start from day one sending tens of thousands of emails, which could be considered spam. Instead, send a small volume of email daily for several days, then increase the volumes gradually. You can find more information on the volume limits on the help pages of the domains you send emails to.

Regularly check the email addresses in your databases

After a certain period of time, the email addresses become invalid because their users could close them, or the services could be closed or resold. Regularly check the health of your recipients' MX records and SMTP servers to limit the bounceback rate of your campaigns. You can do something as simple as checking the emails in your database using a regular expression (regex) specifically to test the validity of an email structure. You can also use the Abstract API or other email verification products at this level. If you're more technical, you can learn how to verify email addresses using PHP, Javascript, Python, Ruby, and more.

Check the trust level of your domains and IP

Regularly verify that any of your domains and IP addresses are not listed in public spam protection black-lists. You can use one of the following tools to verify: DNSbl, Mxtoolbox.

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