Note: This post was updated in 2017 to ensure all best practices for avoiding spam filters are up-to-date for email marketers. 

The world of email deliverability can be a frustrating place. Even the most seasoned and rule-abiding email marketers will experience delivery issues and (accidentally) send spam emails.

In this post, we serve up some of our best advice to ensure that your emails avoid spam filters and get delivered to your recipient’s inbox. For additional information and explanation on the tips below, check out the entire Tips & Tricks to Stay Out of the Spam Folder Guide.

Build your OWN email list

What you say in your emails is incredibly important, but your content doesn’t mean anything if you’re saying it to the wrong or to an unengaged audience. Always avoid:

  • Renting, purchasing, or co-registering an email from a third party
  • Sharing or using a shared list with a partner
  • Scraping emails—if you’re using a robot to collect emails, known as email harvesting, this practice puts you squarely into the spam camp. Don’t ever do it!

Organically building your email list is a long-term play that will benefit your email program. It’s not the easiest or the fastest way, but it’s the most effective.

Provide a double opt-in

When you’re building your email list, consider how you will verify that your recipients want to receive email from you or your brand. For this, you could use a double-opt-in method that provides a subscriber with a welcome email that they must confirm (usually check a box that says they agree to emails) before they officially end up on your email list.

The double opt-in method will demonstrate that your recipient has a genuine interest in your emails (which will keep your engagement and deliverability rates high). Read more about the different types of email opt-in and why double opt-in is preferred in our blog post, You Forgot to Say Please: How to Collect Email Addresses.

Authenticate your email with SPF, DKIM, and DMARC

Email authentication can be tricky, but it’s easiest to remember that authenticating your email verifies that you are who you say you are. Inbox providers, such as Google and Yahoo, trust authenticated email more and are more likely to deliver mail from authenticated email into the inbox.

The following methods authenticate your email and prove to the ISPs that your email is worthy of the inbox and not the spam folder:

The methods above are the responsibility of the sender, but SendGrid can help with each. Learn more about how our professional services can help.

Regularly clean up your email list

Some of your recipients will unsubscribe from your email list, but keep in mind that many who no longer want to receive your email will simply ignore your emails instead of unsubscribing. This is actually harmful because the lower your email engagement rate, the less favorably you will be viewed by the ISPs. This means that your emails are more likely to go to the spam folder.

A smaller, more engaged email list always trumps a large list full of unengaged users.

Combat low engagement by regularly removing unengaged users, bounced emails, and role email addresses. Your email list is going to experience some amount of churn. Don’t take it personally; be proactive, clean up your list, and experience improved email deliverability rates.

Avoid blacklists and monitor your reputation

Your email domain has a reputation associated with it and if it slips or you send an email to a spam trap email, you may find yourself on an email blacklist. Unfortunately, even cautious and well-intentioned senders may find themselves on a blacklist.

Reduce the risk of ending up on a blacklist by considering some of the following practices:

  • Using confirmed opt-in or double opt-in
  • Implementing a sunset policy to remove unengaged subscribers
  • Using real-time address validation—if somebody enters in a false email (or even a typo) and you send email to that invalid email address, your sender score suffers.

Keeping an eye on your delivery rates will notify you of any signals that you may be on a blacklist. For more information on blacklists, read Avoiding Blacklists: Best Practices For Reducing Your Risk of IP and Domain Blacklisting.

Provide a preference center

A preference center allows subscribers to choose how frequently they receive your emails and reduces the risk of them unsubscribing or marking your emails as spam. Provide a simple and prominent preference center to reduce friction and the risk of irritating your recipients.

Each recipient is different and a preference center helps your users find their happy cadence and keeps engagement high. And higher engagement will help you keep your inbox and delivery rates high and help keep your emails from going to spam.

There are several types of preference centers—read about what type is best for your email program.

Monitor email engagement metrics

Tracking your email performance and engagement metrics is the only true way to know if your email program is improving or if some changes are needed. Before you measure though, it’s important to develop some baseline metrics so you have a consistent picture of your email performance.

The following metrics are a good place to start:

  • Spam complaints
  • Open rates
  • Click-through rates

Don’t panic if you start to notice negative trends, but act as quickly as you can. For example, if your open rates are starting to dip, review your subject lines and email frequency as those two variables are likely affecting this metric.

For more advanced metrics, check our 4 Important Email Metrics to Monitor blog post.


Email marketing is far from simple and no matter how hard you try, finding perfection is a fleeting goal. But that doesn’t mean you can’t get close! Following the tips above position your email program to perform its best. Always keep in mind that the higher your email engagement, the more likely your email will end up where it is intended and not get caught in spam filters.

Email is constantly changing and so are best practices, the best thing you can do is make sure you’re up to date on those best practices. Read the entire Top 10 Tips And Tricks to Stay Out Of The Spam Folder Guide to ensure you’re doing everything you can to stay out of the spam folder!

Elmer Thomas is SendGrid's Developer Experience Engineer. His mission is to help SendGrid live up to its slogan: "Email Delivery. Simplified" by improving the lives of developers, both internally and externally. Via all sorts of hackery, of course. Follow his exploits on Twitter and GitHub.