There are numerous reasons why your email could be going to a customer’s spam folder, and this is caused by the mail servers’ built-in spam filters. Spam filters detect unwanted emails and prevent them from being delivered to the recipient’s inbox. These spam filters are frequently updated, so what may not be considered spam today, may be considered spam tomorrow.

So what can we do to combat emails that going into the spam? Here are a few ways to help improve your sending reputation.

Configure DKIM and SPF

Domain Keys Identified Mail (DKIM) and Sender Policy Framework (SPF) are two email authentication methods which can help against email spoofing, phishing, and spam. Having these set up will help improve deliverability by verifying the source of where the email originated.

  • DKIM attaches a digital signature to the email which identifies you as an authorized sender and the recipient server will verify that signature.

  • SPF allows you to specify which email servers are legitimate for your domain and improves deliverability for emails that are sent from your authorized domain.

Test your Deliverability

Many spam checkers will give you a preview rating based on how likely it is to trigger spam filters.

We recommend using Mail-Tester because it gives you an overall rating using SpamAssassin, and also inspects other elements of your email that could affect your deliverability. For example, is your email formatted well? Are your emails authenticated? Is your IP address currently on a blacklist?

Personalize Emails

Spam Filters look for similarities in your emails and increasing the uniqueness of your emails by adding personalized content will help avoid these flags.

Include a Plain Text Version

Most spam filters can detect if there is only an HTML version of the template, this could have a negative impact on the spam rating.

As well as having a better spam rating, it is generally good practice to include a plain text version. Plain text emails are more accessible and easier for users that require a screen reader. Additionally, many older email clients may not support HTML formatted messages.

Image to Text Ratio

Image heavy emails have a high chance of triggering spam filters. Always make sure that your emails have a healthy balance of words and images. We recommend having a 2:1 ratio of words to images. Always include an alt attribute in your image tags.

Videos and Attachments

These media types are often rejected by email clients, and will likely set off spam filters if they are accepted. If you must include an attachment, make sure the attachment file is no bigger then 10MB. With that said, it is always preferable to host the file and include a link for your user to download it.

Many email clients do not support videos in emails, on top of lowered deliverability, they will sometimes flagged the email as malicious content. If you must include a video, we recommend taking a screenshot of the video and linking the image to the video.

Including an unsubscribe link in your emails will help with the deliverability for future emails sends. This works because customers that have an opt-out method will usually use that method if they do not want those emails. If they do not have this method available or cannot easily locate this, they might report the email as spam, thus affecting your deliverability.

Shared IP Addresses

Some ESPs use shared IP addresses instead of dedicated IP addresses when sending your emails. If you are using a shared IP address and someone using the same IP had one of their emails marked as spam, this could affect your sending IP reputation.

Further Reading