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Troubleshooting Common WP Mail SMTP Fatal Errors and Activation Issues

49 threads Sep 16, 2025 Plugin → Wp mail smtp by wpforms

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Encountering a fatal error when activating or using the WP Mail SMTP by WPForms plugin can be a frustrating experience that brings your site to a halt. Based on community reports, these errors often share common causes and solutions. This guide will help you diagnose and resolve the most frequent fatal errors associated with this popular email plugin.

Common Fatal Errors and Their Causes

Users frequently report errors that prevent plugin activation or cause site-wide crashes. The error messages often point to a few specific underlying issues:

  • Missing Database Tables: Errors mentioning tables like wp_actionscheduler_actions doesn't exist indicate the Action Scheduler library couldn't create necessary database tables during activation.
  • File Inclusion Problems: Warnings about missing files like CacheItemPoolInterface.php or PHPMailer.php often suggest incomplete plugin installation or file permission issues.
  • Class Not Found Errors: Messages referencing missing classes such as ActionScheduler_Store_Deprecated or WPMailSMTPCore typically indicate corrupted plugin files or conflicts with other plugins.
  • Translation String Issues: For non-English WordPress installations, errors in files like Conflicts.php on specific line numbers may relate to incorrect translation placeholders.
  • PHP Version Incompatibility: Some errors may occur on outdated PHP versions that lack support for modern PHP features.

Step-by-Step Troubleshooting Solutions

1. Complete Plugin Reinstallation

The most effective first step is a complete clean reinstall:

  1. Access your site via FTP/SFTP or your hosting file manager
  2. Navigate to /wp-content/plugins/
  3. Completely delete the wp-mail-smtp folder
  4. Freshly install the plugin from the WordPress repository
  5. Reactivate and reconfigure your settings

2. Verify WordPress Core Integrity

Since some errors may indicate WordPress core issues:

  1. Go to Dashboard → Updates in your WordPress admin
  2. Click "Re-install version [X.X.X]" to refresh core files
  3. After completion, retry activating WP Mail SMTP

3. Enable Debugging for Detailed Error Information

When error details aren't clear, enable WordPress debugging:

  1. Edit your wp-config.php file via FTP/SFTP
  2. Locate the line: define('WP_DEBUG', false);
  3. Replace it with: 
    define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', false);
@ini_set('display_errors', 0);
  4. Save the file and reproduce the error
  5. Check /wp-content/debug.log for detailed error information

4. Check for Plugin and Theme Conflicts

Temporarily disable other plugins and switch to a default theme:

  1. Rename the plugins folder to plugins.deactivate
  2. Create a new empty plugins folder
  3. Activate only WP Mail SMTP to test if it works alone
  4. If successful, reactivate other plugins one by one to identify conflicts

5. Verify PHP Version Compatibility

Ensure your server meets minimum requirements:

  1. Check your current PHP version in your hosting control panel
  2. Upgrade to at least PHP 7.4 (PHP 8.0 or higher recommended)
  3. Confirm that your hosting environment meets the plugin's requirements

6. Database Table Repair

For missing Action Scheduler tables:

  1. Use phpMyAdmin or similar database tool
  2. Check if tables prefixed with actionscheduler_ exist
  3. If missing, deactivate and delete the plugin
  4. Reinstall fresh - the tables should regenerate during activation

When to Seek Additional Help

If these steps don't resolve your issue, the problem might be more complex. The 'WP Mail SMTP by WPForms' team maintains extensive documentation that covers specific error scenarios. When seeking help in community forums, be prepared to provide:

  • The complete error message from your debug log
  • Your current PHP version
  • WordPress and plugin versions
  • Any recent changes to your site
  • Steps you've already attempted

Most fatal errors can be resolved through methodical troubleshooting. Starting with a complete plugin reinstallation and conflict testing resolves the majority of these issues, allowing you to successfully configure reliable email delivery for your WordPress site.

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