Why Your Emails Go to Spam and How to Fix It

1. Missing or Broken Authentication

The number one cause of deliverability problems is missing email authentication. Modern mail providers (Gmail, Outlook, Yahoo) check three records: SPF, DKIM, and DMARC. If any of these are missing, misconfigured, or failing, your emails are far more likely to be flagged.

SPF verifies the sending server is authorized. DKIM verifies the message has not been tampered with using a cryptographic signature. DMARC ties them together and tells receivers what to do on failure.

Fix: Use our Email Checker to see which records are missing or broken. Then follow our SPF guide and DMARC guide to fix them.

2. Poor Sender Reputation

Every sending IP and domain builds a reputation over time. If your IP has been used to send spam in the past (common with shared hosting), or if recipients frequently mark your emails as spam, your reputation degrades. Major providers maintain internal sender scores that heavily influence filtering decisions.

Fix: Use a reputable transactional email service (SendGrid, Postmark, Amazon SES) instead of sending from your web server directly. Monitor bounce rates and keep them below 2%. Remove unengaged subscribers regularly.

3. Spammy Content Patterns

Content-based filtering has evolved far beyond simple keyword matching, but certain patterns still trigger spam filters:

• ALL CAPS subject lines or excessive exclamation marks
• Image-heavy emails with very little text
• URL shorteners (bit.ly, t.co) in the email body
• Misleading subject lines that do not match the content
• No unsubscribe link (required by CAN-SPAM and GDPR)
• Sending HTML-only emails without a plain-text alternative

4. No Reverse DNS (PTR Record)

If you are sending from your own server, the IP address must have a valid reverse DNS (PTR) record that matches your sending domain. Without it, many mail servers will reject your email outright. This is especially important for VPS and dedicated server setups.

Fix: Contact your hosting provider to set up a PTR record for your server's IP. Use the CheckFast DNS Checker to verify the PTR record resolves correctly.

5. Blacklisted IP or Domain

Public blacklists (Spamhaus, Barracuda, SURBL) maintain lists of known spam sources. If your sending IP or domain appears on one, many receiving servers will automatically reject or spam your messages. This can happen even if you have never sent spam — for example, if your IP was previously used by a spammer.

Fix: Check major blacklists using the CheckFast Email Checker. If listed, follow the delisting process for each blacklist. Most require you to fix the underlying issue and submit a removal request.

6. Sending to Purchased or Stale Lists

Purchased email lists are spam traps waiting to happen. Even if the addresses were once valid, many will have been converted into spam traps by providers. Hitting a single spam trap can tank your sender reputation. Similarly, sending to addresses that have not engaged in months leads to high bounce and complaint rates.

Fix: Only send to people who explicitly opted in. Implement double opt-in. Regularly clean your list by removing hard bounces and unengaged contacts (no opens in 90+ days).

The Deliverability Checklist

• SPF record is valid and includes all sending services
• DKIM is configured for every sending service
• DMARC policy is published (at minimum p=none with rua)
• Reverse DNS is set up for sending IPs
• Not on any major blacklists
• Bounce rate is below 2%
• Complaint rate is below 0.1%
• Unsubscribe link is present in every marketing email
• Plain-text alternative is included