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Why Are My Emails Going to Spam? Troubleshooting Post SMTP Deliverability Issues

37 threads Sep 16, 2025

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Are Your WordPress Emails Landing in Spam?

If you've configured the Post SMTP plugin but find your messages are consistently being flagged as spam or not delivered at all, you're not alone. This is a common frustration for many WordPress site owners. Based on community support threads, this guide will walk you through the most likely causes and how to fix them.

Why Does This Happen?

Email service providers (like Gmail, Outlook, etc.) use sophisticated filters to protect users from spam. When an email fails their authentication checks or comes from a server with a poor reputation, it's often quarantined. The Post SMTP plugin itself doesn't cause emails to be marked as spam; the issue almost always lies in how your server or domain is configured to present itself to the world.

Common Causes and Solutions

1. Missing or Incorrect DNS Records (SPF, DKIM, DMARC)

This is the most frequent cause of deliverability problems. These records act like a passport for your emails, verifying that they are legitimately sent from your domain.

  • SPF (Sender Policy Framework): Lists the servers authorized to send email on your domain's behalf.
  • DKIM (DomainKeys Identified Mail): Adds a digital signature to each outgoing email, proving it wasn't tampered with.
  • DMARC (Domain-based Message Authentication, Reporting & Conformance): Tells receiving servers what to do with emails that fail SPF or DKIM checks (e.g., quarantine or reject them).

How to Fix It: You must add these records to your domain's DNS settings. Your email service provider (e.g., Gmail, Office 365, Brevo) will have documentation on the exact values you need to set. Use a tool like MXToolBox to verify your records are set up correctly.

2. Poor Sender Reputation

If your server's IP address or domain has been used to send spam in the past, it can be blacklisted, causing all outgoing mail to be treated with suspicion.

How to Fix It: Check if your IP or domain is on a blacklist using MXToolBox's blacklist check. If you are listed, follow the instructions on the blacklist's website to request removal.

3. Misconfigured "From" Address

As seen in one thread, emails were being sent from a default [email protected] address instead of the address configured in Post SMTP. This is a classic red flag for spam filters.

How to Fix It: Double-check your settings in Post SMTP > Settings > Message. Ensure the "From Email" address matches the domain you are sending from and is an address you control. The 'From Address' defined in WordPress general settings should also be set to this same domain.

4. Content Triggering Spam Filters

Certain words, phrases, or formatting (e.g., excessive use of exclamation points, all caps, or spam-associated keywords) can trigger filters.

How to Fix It: Use a tool like Mail Tester. Send an email from your site to the address they provide, and you will receive a detailed score and report on what might be causing issues.

5. Using a Trial or Restricted Account

Some email services, like certain Office 365 plans, may impose sending limits or restrict outgoing mail to administrators only for trial accounts, generating errors like #MS42225.

How to Fix It: Verify the terms of your email service plan. You may need to upgrade your account or adjust its settings to permit sending to external recipients.

Diagnostic Steps

If you're still stuck, gather this information to help troubleshoot:

  1. Run the Post SMTP Diagnostic Test (found in the plugin dashboard) and share its report.
  2. Check the Post SMTP Email Log for any specific error messages next to failed sends.
  3. Temporarily disable other plugins to rule out a conflict that might be causing multiple sends or altering email headers.

Final Thoughts

Successfully delivering email from WordPress is a multi-step process involving your plugin, your web server, your email service, and your domain's DNS. By methodically working through these common authentication and configuration issues, you can significantly improve your email deliverability and ensure your important messages reach the inbox.

Related Support Threads Support