Troubleshooting why emails go to spam

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You will learn

Learn about common reasons for emails to go to the spam folder.

Understanding the elements of your email that increase your likelihood of being delivered to the spam folder can help your sender reputation and your subscriber engagement rates.

Before you begin

Klaviyo is responsible for sending your emails, but once these emails are in the hands of the inbox provider (i.e. Gmail or Yahoo), the messages are filtered according to each provider’s rules. All inbox providers have a built-in system that scans incoming emails, and automatically sorts them using complex algorithms that are not made public. 

For more information on email deliverability and best practices, see our guide on understanding email deliverability.

While inbox providers do not report the specific reason an email was placed into spam, there are common triggers that you should keep in mind when sending. If you are seeing emails go to spam, identify if any of the following triggers are potentially contributing. 

Email content

Inbox providers use spam filters to determine whether or not your emails reach the inbox. While it’s possible to observe trends in spam filter behavior, spam filters are designed so that evading them can’t be perfected.

Here are a few ways you can be smart about your email content:

  • Avoid “spammy” subject lines.
    A lot of words can potentially trigger spam filters; thus, we’ve compiled some dos and dont's regarding subject line word choice. In general, avoid using all capital letters. Studies show that 85% of recipients prefer an all-lowercase subject line to one in all caps. Both all caps and excessive exclamation points can trigger spam filters. Avoid things like:
    • Using a lot of symbols!!!!!********
    • Including just one large image in your email
    • Implementing eye-catching or spam triggering phrases like "JUST THIS ONCE FOR A LIMITED TIME ONLY", "100% FREE!", "ACT NOW!"
  • Find a balance between images and text.
    Emails that consist solely of GIFs and images (or are very image-heavy) may trigger spam filters. Instead, emails should contain a combination of images and text. Spammers often use images to avoid spam trigger words, but inbox providers have evolved faster. Email on Acid found that emails should contain at least 500 text characters to avoid being sent directly to spam. If this is an issue for you, consider including contact information, legal disclaimers, an unsubscribe link, or a company address in fine print at the bottom of your email. Also, include alt text for your images so subscribers can read a description if your images don’t load properly. Alt text is also crucial to ensure that your emails are accessible.
  • Limit the number of URLs.
    Large amounts of hyperlinked text can be considered a red flag for inbox providers. Spammers typically include as many links as possible, both hidden and overt. While including a few well-placed links probably won't cause any problems, consider only including necessary links and avoid overuse, especially if you link to sites other than your own.
  • Avoid unnecessary code in your templates.
    If you use our drag-and-drop template editor, we take care of this for you. If you're coding your own HTML templates or editing the source code of text blocks within our template editor, note that extra tags and poor code can trigger spam filters. Copy and pasting text from certain softwares like Microsoft Word can bring over styling that increases the code weight. To paste copied text without the associated styling, use Ctrl + Shift + V as a keyboard shortcut on Windows, and Cmd + Shift + V on Mac OS. 
  • Get personal in your messaging.
    The more personalized your emails are, the more likely email clients are to deem them important and subscribers may be more inclined to open as well. If an email client determines that you likely know the person you're sending to, this significantly lowers the risk of your email ending up in spam. Klaviyo makes it easy to insert a recipient's first name into the subject line and body of an email. You can also ask your contacts to add you to their address books, or try using plain text emails as opposed to formatted ones. When in doubt, run your email templates through free spam filter tools online like Mail Tester. This can help flag issues with your content that may cause email clients to flag your emails.
  • Add 2 unsubscribe links or buttons.
    Consider adding an unsubscribe link to the top of your email and to the bottom. Letting people opt out when they no longer want to receive emails will reduce spam complaints and increase open rates over time as you begin to send to a more engaged list overall. While you don't want high unsubscribe rates, you'd much rather someone unsubscribe than mark your email as spam.This will also help in cases where emails may be clipped because they are too large. 

Email authentication issues

Mail servers use email authentication protocols to verify that incoming emails are from legitimate senders, protecting your brand and your customers from malicious actors. The most commonly used email authentication standards are SPF, DKIM, and DMARC.

If your emails fail this verification, it can cause your emails to be rejected or to be placed in spam. Determine if your brand is using a DMARC policy and make sure that it is valid.

In order to be DMARC compliant, you need to connect a dedicated sending domain to your account that matches the domain in your sender email address (i.e. your from address). For instance, if you send an email using as the from address and is protected by DMARC, your account will need to use a dedicated sending domain like to meet DMARC requirements.

In addition to preventing phishing and spoofing attempts, implementing these protocols can help improve deliverability, as mailbox providers will be able to confirm the identity of the sender. 

Sender reputation 

Sender reputation is a measure of how inbox providers evaluate your trustworthiness as a sender. This determines how emails are sorted, and is crucial to any email marketer. With a poor sending reputation, inbox providers can send the sender’s email straight to spam.

When inbox providers determine the sender reputation for each domain or IP, each provider evaluates various metrics. Some of the main metrics that contribute to the score include: 

  • Engagement (e.g., open rates and click rates)
  • Sending volume and frequency (i.e., how many emails are being sent at once and how often they send)
  • Bounce rates
  • Spam complaints 
  • Unsubscribe rates


Not only should you send to opted-in contacts only, you should also aim to send to engaged subscribers to avoid hurting your deliverability performance. To isolate engaged subscribers, create an engaged segment; then, target this segment when sending campaigns.

If you are seeing your emails getting placed in spam or junk, we highly recommend comparing your performance to these benchmarks to check if low engagement rates may be contributing towards deliverability issues. 

Sending volume and frequency 

Sending too many emails to a mail server during a short time frame can result in rejections and the placement of emails in spam. Creating a sending schedule based on customer engagement is key to achieving strong open rates and maintaining a positive relationship with your subscribers. Sending too often to unengaged profiles will hurt your sender reputation, whereas sending too infrequently to engaged customers is leaving money on the table. It's best to achieve a happy medium through the use of segments and sending schedules. 

Bounce rates

One of the factors that inbox providers consider when determining how to place your emails, is the bounce rate associated with your brand. A bounce occurs when an email is either not successfully delivered or is rejected by the recipient's email provider. If your account has a high number of bounces, this can have a negative impact on your deliverability performance and your sender reputation. It is important to monitor this metric and take action when you see a rise in this rate.

Spam complaints 

Spam complaint rates measure how often recipients mark your emails as spam. A high spam complaint rate is something to act upon immediately as this will hurt your deliverability performance and sender reputation. 

Unsubscribe rates 

Unsubscribe rates inform you of how often customers unsubscribe from your emails. A high unsubscribe rate indicates that you’re either sending to those who do not wish to receive your marketing or you’re sending content that does not resonate with this audience.

Unsubscribe rates also impact your deliverability performance, so it is important to monitor this metric and take action to lower unsubscribes.

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