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Foundational

How to Keep Your Emails Out of Spam Folders

Brad Slavin
Brad Slavin CEO & Founder
Updated April 17, 2026

Quick Answer

Three things cause emails to land in spam folders: spammy content, missing authentication, and sending from servers with bad reputations. To avoid spam folders, check email content with spam-testing tools before sending, authenticate all outbound email with SPF, DKIM, and DMARC, and send only from clean IP addresses backed by a zero-spam policy with outbound spam filtering.

Mail server anti-spam protection

It doesn’t do you any good to develop an opt-in email list of interested prospects if the emails they want end up in their spam folder.

In general, there are three things that make an email look spammy:

  1. If the email contains spammy content
  2. If the email is not authenticated
  3. If the email was sent from a spammy email server

If you protect the emails you send from these three things, you should have a very high delivery rate.

Check for Spammy Content Before Sending

Unless you’re intentionally sending spam, you probably don’t need to avoid using obviously spammy words. But that doesn’t mean you may not unintentionally send an email with spammy content.

Avoid stuffing your email with keywords and useless content. There are tools available that check your email for spammy content — you just send your email to a designated address and view your report.

Only Send Authenticated Emails

Three technologies enable email senders to send authenticated emails. Authenticated emails are trusted emails, especially by ISPs, who have the power to filter your emails into their spam folders.

The first technology is SPF, or Sender Policy Framework. SPF allows the receiving mail server to check during mail delivery that a mail claiming to come from a specific domain is submitted by an IP address authorized by that domain’s administrators.

The second technology is DKIM, or DomainKeys Identified Mail. DKIM is an email authentication method designed to detect forged sender addresses in emails.

The third technology, DMARC, or Domain-based Message Authentication, Reporting and Conformance, ties the other two technologies together. DMARC is designed to give email domain owners the ability to protect their domain from unauthorized use.

If you want to keep your emails out of spam folders, you need to keep ISPs happy. Using any one of these technologies will increase the trust factor of outbound email. But using all three together will maximize your chances of keeping your emails out of spam folders.

Only Send Emails from Clean IPs and Email Servers

When an email server gets a bad reputation for sending out spam, both the IP address of the server and email domain end up on a blacklist. Once they’re on a blacklist, anything coming out of that IP or from that domain has a hard time avoiding the spam folder.

The challenge here comes when you use a shared email hosting provider. You may not be sending out spam, but if someone else using that server does, that IP will be blacklisted which will directly affect your ability to send email.

When you use a shared outbound SMTP service, make sure they have a zero spam policy that blocks or restricts messages that would damage the reputation for everyone using that service. Outbound spam filtering is an essential best practice to keeping your emails out of spam folders.

Summary

If you’re going to send out a large number of emails, you may as well take the time to make sure they avoid the spam folder. A quality outbound SMTP provider employs the full suite of email authentication technology (SPF, DKIM and DMARC), optimizes your sending routes, and closely monitors IP reputations to ensure the best possible delivery rate. A zero spam policy that allows blocking or restricting messages that would damage reliability or reputation is essential.

Brad Slavin
Brad Slavin

CEO & Founder

CEO & Founder of DuoCircle. Expert in email deliverability, authentication, and enterprise SMTP infrastructure.

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