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How spam complaints work

Spam complaints are reports made by email recipients against emails they don't want in their inbox. It's important to understand how spam complaints work, and how to do your best to avoid them, because even legitimate senders get complaints.

An email that receives an excessive number of complaints, could result in your next email being blocked by ISPs, so that even people who do want to hear from you may not.

Industry standard for spam complaints is less than 0.1%. That's about one complaint for every 1,000 recipients.

How spam complaints are made

Most mailbox providers, sometimes known as ISPs, include a prominent "This is Spam" button in the inbox to allow people to report unwanted emails. Here's an example "spam" button in an AOL account:

People click the spam (or junk) buttons for various reasons. It may be that they're confused about who you are, or why you're emailing them, or it could be because they can't find the unsubscribe link.

What happens when we receive complaints

As an email service provider (ESP), we have what is called a "feedback loop" with all of the major ISPs, for example: Yahoo,, Comcast. When a recipient marks an email as spam, their ISP notifies us through the feedback loop.

Recipients who report your email as spam are immediately unsubscribed from your audience, meaning you will no longer be able to send emails to that contact.

Every complaint received is recorded in our system, and we regularly calculate the percentage of complaints generated by each email.

We also monitor complaints made by Gmail customers, however the feedback loop with Gmail works a little differently.

Higher-than-normal complaints

If you send an email that receives more than a 0.2% complaint rate, we will notify you with a warning email that includes advice to help you address the situation.

We understand that even legitimate senders get complaints so, provided you're doing the right thing, do not be alarmed if you get a warning email from us.

If complaints for a single email exceed industry thresholds — anything above 0.4% — your account will be suspended in order to prevent your sender reputation from further damage.

Tips for preventing complaints

The best ways to avoid your emails being marked as spam are:

  • Set up a custom domain, so the domain used in your tracking links matches the one in your from address.

  • Keep a permission-based audience.

  • Never buy, rent or borrow subscriber lists, as these are not permission-based and can contain spam traps.

  • Use a confirmed opt-in list to stop fake signups, bots and spelling errors from sending your emails where they're not wanted.

  • Make sure your "From" details mention the business the email is coming from.

  • Keep content relevant by using personalization and dynamic content.

  • Let contacts know how often you'll be sending.

  • Don't overwhelm your contacts with too many emails.

  • Don't send so few emails that contacts don't remember signing up.

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