How to Fix SMTP Email Sending Issues in WordPress (Full Guide)

Why WordPress Emails Fail?

Out of the box, WordPress relies on the PHP mail() function to send emails such as password reset links, contact form submissions, and order notifications.

However, in many hosting environments, this function is unreliable, blocked, or poorly authenticated, which leads to emails:

• Not being delivered
• Being marked as spam
• Or getting silently dropped by receiving servers

This is a critical issue—especially for eCommerce, membership, and lead generation sites—where email delivery is essential.

What Is SMTP and Why It Solves the Problem?

SMTP stands for Simple Mail Transfer Protocol. It’s the standard protocol used to send emails via authenticated and secured servers.

Using SMTP ensures:

• Emails are sent through a real email server (not just from your web server)
• Authentication (username/password) is used
• Messages pass through anti-spam filters more reliably
• SPF, DKIM, and DMARC validations are respected

PHP Mail vs SMTP

Step 1: Install a WordPress SMTP Plugin

To fix this issue, you need to route WordPress emails through SMTP using a plugin.

Top SMTP Plugins for WordPress:

• WP Mail SMTP (by WPForms) – Most popular, easy setup, supports multiple SMTP providers
• Post SMTP – Has advanced debugging and fallback options
• FluentSMTP – Fast, lightweight, and privacy-focused

We’ll use WP Mail SMTP in this tutorial.

Installation Steps:

• Go to Plugins > Add New
• Search for: WP Mail SMTP
• Click Install and then Activate

Step 2: Choose an SMTP Email Provider

You need to use a real email service that provides SMTP credentials.

For serious websites, we recommend domain-based providers like SendGrid, Mailgun, or SMTP2GO.

Step 3: Configure SMTP Plugin Settings

After installing WP Mail SMTP:

1. Go to WP Mail SMTP > Settings

2. Under Mailer, choose:

• “Other SMTP” if using custom provider (e.g., Mailgun, SendGrid)
• “Gmail” if using Gmail (requires OAuth or App Password)

3. Fill in the SMTP details:

Step 4: Send a Test Email

To confirm everything works:

• Go to WP Mail SMTP > Tools > Email Test
• Enter an email address (preferably Gmail or your own)
• Click Send Email

If successful, you’ll see:

“The test email has been sent successfully!”

If failed, error logs will guide you (e.g., connection refused, authentication failed).

Step 5: Ensure DNS Records Are Correct (SPF, DKIM, DMARC)

To ensure email deliverability, configure DNS records for your domain:

• SPF: Tells email servers which IPs can send on behalf of your domain
• DKIM: Authenticates that emails haven’t been tampered with
• DMARC: Policy framework to block fake emails

Example DNS records for Mailgun:

SPF:  v=spf1 include:mailgun.org ~all  
DKIM:  k=rsa; p=MIGfMA0GCSq...  
DMARC: v=DMARC1; p=none; rua=mailto:admin@yourdomain.comCode language: HTTP (http)

Contact your domain registrar or use Cloudflare to add these records.

Step 6: Common SMTP Errors and Fixes

Step 7: Enable Email Logging for Debugging

Install an email log plugin like:

• WP Mail Logging
• Post SMTP (has built-in logs)

Benefits:

• View email delivery history
• Debug failed messages
• Confirm which plugin sent the email

Step 8: Use Domain Email (Not Gmail Free Address)

Always use domain-based emails like:

• ✅ admin@yourdomain.com
• ❌ mywebsitename@gmail.com

Why?

• Gmail/Outlook free accounts are limited or blocked for business use
• Many SMTP services reject generic addresses in From headers
• Better branding and authentication

Use Transactional Email Services for Reliability

If you send a lot of emails (eCommerce, memberships), use a dedicated transactional email API:

These services ensure high delivery rates, detailed logs, and bounce management.

Ensure Reliable Email Delivery in WordPress

SMTP is the only professional way to send emails in WordPress today. Avoid relying on the outdated mail() function that leads to undelivered messages.

To summarize:

• Use WP Mail SMTP or equivalent plugin
• Set up a trusted SMTP service (like SendGrid, Mailgun, Gmail)
• Configure DNS records (SPF, DKIM, DMARC)
• Test your setup regularly
• Use email logs for debugging

Your site depends on emails. Make them reliable, secure, and fast.