Nothing is more frustrating than hitting “send” on a critical email, only to have it vanish into the dreaded spam folder. Whether you're running an email marketing campaign, sending invoices, or even just sharing project updates, poor email deliverability can damage your business reputation and disrupt communication.
If you're wondering “Why are my emails being marked as spam?”, you're not alone. The issue often stems from a mix of technical misconfigurations, poor sender reputation, and content-related factors. The good news? Most of these problems are fixable.
In this guide, we'll dive into the technical reasons why your emails might be flagged as spam and offer step-by-step solutions to get your messages back into the inbox.
1. Missing or Misconfigured Email Authentication (SPF, DKIM, DMARC)
The Problem:
One of the most common technical reasons for emails landing in spam is missing or incorrect email authentication. Without proper authentication, receiving mail servers can’t verify that your emails are from a trusted source, and they’ll often mark them as spam or block them entirely.
Key Email Authentication Protocols:
SPF (Sender Policy Framework): Specifies which IP addresses are authorized to send emails on behalf of your domain.
DKIM (DomainKeys Identified Mail): Adds a cryptographic signature to your emails, proving they haven't been tampered with during transmission.
DMARC (Domain-based Message Authentication, Reporting, and Conformance): Builds on SPF and DKIM to tell receiving servers how to handle unauthenticated emails.
How to Fix It:
Set Up SPF Records:
Create a TXT record in your DNS with the SPF policy.
Example SPF record:
dnsCopyEditexample.com IN TXT "v=spf1 include:_spf.google.com ~all"
Use the include mechanism to authorize third-party services (like Google, Mailchimp, etc.).
Implement DKIM Signing:
Enable DKIM in your email service provider’s settings.
Add the DKIM public key to your DNS.
dnsCopyEditgoogle._domainkey.example.com IN TXT "v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY"
Configure DMARC Policies:
Add a DMARC record to instruct mail servers on how to handle failing emails.
dnsCopyEdit_dmarc.example.com IN TXT "v=DMARC1; p=reject; rua=mailto:[email protected]"
Test Your Authentication:
Use tools like Your DMARC to verify your SPF, DKIM, and DMARC configurations.
bashCopyEditdig +short TXT example.com
2. Poor Sender Reputation
The Problem:
Email providers track your sender reputation based on factors like spam complaints, bounce rates, and engagement metrics. A poor reputation can cause even legitimate emails to be flagged as spam.
How to Fix It:
Monitor Blacklists:
Check if your IP or domain is on any blacklists using tools like Your DMARC Blacklist Checker.
bashCopyEditdig +short example.com | xargs -I {} curl https://blacklist-check.example.com/{}Warm Up Your IP:
If you're using a new IP address, gradually increase the volume of sent emails to build trust with ISPs.
Reduce Bounce Rates:
Regularly clean your email list to remove invalid addresses. High bounce rates can trigger spam filters.
Monitor Spam Complaints:
Use feedback loops provided by ISPs to monitor complaints and remove recipients who mark your emails as spam.
3. Content Triggers in Your Emails
The Problem:
Spam filters scan email content for suspicious phrases, excessive links, and poor formatting. Even small mistakes can trigger filters.
Common Content Mistakes:
Overuse of spammy words like “FREE,” “LIMITED TIME,” or “GUARANTEED.”
Too many images and not enough text.
Broken HTML or missing plain-text versions.
Excessive use of links or shortened URLs.
How to Fix It:
Write Clear, Professional Content:
Avoid using all caps and too many exclamation points.
Ensure a healthy text-to-image ratio (ideally, more text than images).
Use Clean HTML:
Avoid copying content directly from Word or other editors, which can insert messy code.
Always include a plain-text version of your email.
Limit Links and Trackers:
Use only essential links, and avoid URL shorteners that can look suspicious.
Test your emails with tools like Mail Tester or GlockApps.
4. Sending from a Shared IP Address with a Bad Reputation
The Problem:
If you’re using a shared IP address from your email service provider (ESP), your reputation can be affected by other senders on the same IP.
How to Fix It:
Switch to a Dedicated IP:
Many ESPs offer dedicated IPs for better deliverability control.
Warm up the new IP gradually to build reputation.
Choose a Reliable ESP:
Use reputable providers like Google Workspace, SendGrid, or Amazon SES that maintain good IP hygiene.
5. Not Setting Up Reverse DNS (PTR Records)
The Problem:
Reverse DNS (rDNS) translates an IP address back to a domain name. If rDNS isn’t set up, many mail servers will reject your emails or mark them as spam.
How to Fix It:
Configure a PTR Record:
Contact your hosting provider or ESP to set up a PTR record that points your IP to your domain.
dnsCopyEdit192.0.2.1.in-addr.arpa IN PTR mail.example.com.
Verify rDNS Setup:
Use the following command to verify:
bashCopyEditdig -x 192.0.2.1
6. High Sending Volume Without Proper Throttling
The Problem:
Sending a large volume of emails in a short period can trigger spam filters, especially if the recipients weren’t expecting your message.
How to Fix It:
Throttling Email Sends:
Space out large email campaigns over time.
Use rate limiting to send emails in smaller batches.
Segment Your Email List:
Target smaller, more specific groups of recipients.
Personalize content to increase engagement and reduce spam complaints.
7. Your Domain or IP is Blacklisted
The Problem:
If your domain or IP address is on a blacklist, ISPs will likely mark your emails as spam or block them entirely.
How to Fix It:
Check Blacklist Status:
Use tools like MXToolbox or Your DMARC Blacklist Checker to see if you’re listed.
Request Delisting:
If you find your IP or domain on a blacklist, follow the provider’s process to request removal.
Prevent Future Blacklisting:
Follow best practices for sending emails.
Monitor your email deliverability regularly.
8. Lack of Engagement from Recipients
The Problem:
Email providers use engagement metrics like open rates, click-through rates, and reply rates to determine if your emails are valuable. Poor engagement signals to ISPs that your emails might be unwanted.
How to Fix It:
Re-Engage Inactive Subscribers:
Send re-engagement campaigns to inactive users.
Remove unresponsive recipients from your list.
Encourage Interaction:
Ask questions or request feedback to prompt replies.
Personalize subject lines and content for better engagement.
Final Thoughts
Email deliverability isn’t just about writing good content—it’s about getting the technical foundations right. From configuring SPF, DKIM, and DMARC to monitoring your sender reputation and avoiding content triggers, the path to the inbox requires a comprehensive approach.
By following the steps outlined in this guide, you’ll be able to troubleshoot why your emails are landing in spam and implement practical solutions to ensure they reach your recipients’ inboxes.