How to reduce spam complaint rates

You will learn

Learn about spam complaint rates, and how you can reduce them.

Spam complaint rates measure how often recipients mark your messages as spam. A high rate needs immediate action, as it will hurt your deliverability and sender reputation.

What is a spam complaint rate?

Spam complaint rates measure how often subscribers mark your emails as spam. The formula for calculating spam complaint rate is:

• Spam complaint rate = (Number of reported spam complaints / Number of emails delivered) × 100

Not all inbox providers share individual spam complaints with email service providers (ESPs) like Klaviyo. Gmail does not share these reports. As a result, the rate in Klaviyo does not capture every complaint, and even a very small percentage can indicate an issue.

Spam complaints might not appear on a customer’s profile in Klaviyo, depending on their inbox provider. For this reason, Google recommends using Google Postmaster Tools to monitor your spam complaint rate for Gmail. Google Postmaster Tools reports user-marked spam for personal Gmail accounts, rather than all messages automatically filtered to spam.

Why spam complaint rates matter

When someone marks your emails as spam, this signals to inbox providers that you’re sending content to people who do not wish to receive it, and they will be more likely to send your emails directly to spam rather than an inbox in the future.

Spam complaints are more serious than when someone unsubscribes from your marketing, and a rise in spam complaints should not be taken lightly. To maintain a good sender reputation, monitor spam complaint rates closely, and when you see a rise, take action immediately to lower this metric.

An ideal spam complaint rate is as close to zero as possible, and trending downward if previously high.

How to decrease spam complaint rates

Some key strategies to decrease spam complaint rates include:

1. Optimize your sign-up pages and confirmation messages
2. Enable double opt-in
3. Make your unsubscribe link easily accessible
4. Enable global unsubscribes
5. Try to avoid “spammy” or non-relevant subject lines
6. Ensure your emails are easily discernible as coming from your brand
7. Confirm that your emails render for all users
8. Monitor and adjust your lists
9. Evaluate sending frequency and segment by engagement

You can learn more about each of these strategies below.

1. Optimize your sign-up pages and confirmation messages

To reduce spam complaints, start by designing clear, well-branded sign-up pages.

Your sign-up forms should set clear expectations about what subscribers are signing up for, especially if you have sub-brands or different product lines they could receive emails from. Include details like:

• The channels you’ll contact them through (email/SMS)
• How their information will be used
• The type of content they’ll receive

Consider using a preference page to let subscribers choose the types of content and frequency they prefer. This helps align what they expect with what you send.

Use a confirmation message to tell subscribers that they have signed up to receive emails from your brand. If you use double opt-in, tell them to confirm their subscription by email or text.

Setting clear expectations reduces the likelihood of subscribers marking your emails as spam later on.

2. Enable double opt-in

Double opt-in is the process through which a new subscriber must confirm their subscription before being added to your list. New email lists use your account’s default opt-in setting, so check the setting for each list. It is highly recommended to keep double opt-in on unless you have a specific use case that calls for single opt-in.

To enable double opt-in:

1. Navigate to Audience > Lists & segments and open your list.
2. Select Settings > Consent.
3. Under Opt-in process, select Double opt-in.
4. Click Save.

Learn more about the double opt-in process.

3. Ensure your unsubscribe link is easily accessible

Always include an easy to find unsubscribe link in your emails. If someone can’t easily find this link to opt-out, they’re more likely to mark your email as spam, which has a larger negative impact than an unsubscribe.

Avoid hard-to-read unsubscribe links (e.g., light text on a white background, or buried in text). Instead, place this link at the end of your emails, or at the beginning if you know you have a high mobile audience, and make the colors stand out for ease of reading and accessibility.

Additionally, ensure that your unsubscribe is working and easy to use. Do not place your unsubscribe link buried deep in your footer without room to click or tap easily. Make sure that your subscribers have enough room to click this and that it launches an active and working unsubscribe page.

It’s also helpful to add an update preferences link to your unsubscribe page so subscribers can choose the types of emails they want or their desired frequency. Keep the option to unsubscribe from all email marketing easy to find, without requiring subscribers to click through preference options. If a subscriber adjusts their preferences instead of completely unsubscribing, follow those preferences when you send to them in the future.

4. Enable global unsubscribes

We also highly recommend that you enable global unsubscribes for your lists in Klaviyo. When global unsubscribes are enabled for a list, anyone who unsubscribes from an email sent to that list will be unsubscribed and suppressed from future email marketing across your account.

To enable global unsubscribes:

1. Navigate to Audience > Lists & segments and open your list.
2. Select Settings > Consent.
3. Under Opt-out process, select Unsubscribe from all email marketing.
4. Click Save.

Globally unsubscribed or suppressed profiles cannot receive email marketing, but they can remain on other lists. To remove globally suppressed profiles from a list, open the list and select Manage list > Remove suppressed profiles, then confirm by clicking Remove from list.

If global unsubscribes are turned off for both your account and the list, someone who unsubscribes from a list-based email may still receive emails from other lists or flows. They may assume they have opted out of all email marketing from your brand and mark further emails as spam. As a result, it is best to enable global unsubscribes within list settings.

To share a global unsubscribe link, open your account menu and select Settings > Other > Consent pages. In the Global unsubscribe page section, copy the URL and send it to the subscriber. They can use the page to unsubscribe from all future email marketing from your account.

5. Try to avoid “spammy” or non-relevant subject lines

Another best practice to potentially lower spam complaint rates is to avoid subject lines that may sound like they come from spammers. Not only will this cause your recipients to think you are spam and mark your emails as such, but this may also raise suspicion among inbox providers.

Inbox providers have spam filters that automatically send suspicious emails to the spam folder rather than the inbox. In general, avoid the following spam-triggers:

• All capital letters (e.g., FREE MONEY NOW)
• Excessive special characters, symbols, or emojis (e.g., +++100% FREE MONEY!!)
• Eye-catching or spam-triggering phrases (e.g., JUST THIS ONCE FOR A LIMITED TIME ONLY or ACT NOW!!!)

Instead, craft subject lines that align with your audience's wants and needs. For example, using emojis that do not align with your brand or what a customer is expecting to receive information on, may be seen as spam. Additionally, misleading subject lines that do not align with what the customer originally signed up for or expected could lead to more spam complaints. Continue to A/B test, refine, and review your analytics data to see what subject lines resonate with each of your specific audiences.

6. Ensure your emails are easily discernible as coming from your brand

If you have set expectations correctly on your sign-up pages or forms, customers should be aware they will hear from your brand. With this in mind, you want to ensure that your email sender information is easily recognizable. While an email from an employee in your company may seem personal, especially for new subscribers, they may not know who this email is from and quickly delete it. If you are using a personal name as your sender name, make sure that your subject line or preview text clearly indicates your brand name.

If you would like to remove mention of your specific brand name from the sender information, preview, and subject line, you can do this later in a nurture sequence, after subscribers are familiar with you as a sender.

7. Confirm your emails render for all users

Always account for mobile and desktop displays of your emails. If there are issues on either layout, then customers who see the improperly rendered emails are more likely to mark them as spam, especially if they cannot access your unsubscribe link.

A higher-than-usual spam complaint rate may also signal email clipping. For example, Gmail generally clips emails larger than 102 KB on desktop, and mobile limits can be lower. Adjust your email design to reduce the message’s code size and keep your unsubscribe link visible.

You can use third-party tools like Litmus to preview your email across devices and inbox providers to avoid issues.

8. Monitor and adjust your lists

While refining your list growth and email marketing strategies is important, it’s also key to regularly clean your email lists to maintain healthy engagement.

For lists you haven’t emailed in over about 3 months, or lists you have never emailed that are over about 6 months old, start with 1–2 campaigns to reintroduce your brand before resuming regular sends. Make your brand name prominent in your sender information and your unsubscribe link easy to find. After these campaigns, suppress or delete profiles that still do not engage.

9. Evaluate sending frequency and segment by engagement

Consider using a sending schedule based on email engagement. This is key to achieving strong open rates and maintaining a positive relationship with your subscribers.

Sending too often to unengaged profiles makes recipients more likely to mark messages as spam, whereas infrequent sends to engaged customers may miss opportunities. It's best to achieve a happy medium through the use of segments and sending schedules.

Additional resources