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Fixing Common Post SMTP Plugin Issues: A Troubleshooting Guide

40 threads Sep 17, 2025

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Common Post SMTP Plugin Issues and How to Resolve Them

The Post SMTP plugin is a powerful tool for managing WordPress email delivery, but like any complex software, users may occasionally encounter issues. Based on community reports and troubleshooting threads, here are some of the most common problems and their solutions.

1. PHP Deprecation and Error Notices

Problem: Users on newer PHP versions (particularly PHP 7.4+) may see deprecation warnings or "Illegal String Offset" errors in their admin area or debug logs. These often relate to changes in PHP function parameters or outdated library code.

Solution:

  • Ensure you're running the latest version of Post SMTP, as the development team frequently addresses PHP compatibility issues.
  • Check your PHP error logs for specific file references, which can help identify if the issue is in the core plugin or third-party libraries like the Google API client.
  • Temporarily enable debug logging in WordPress by adding define('WP_DEBUG', true); to your wp-config.php file to gather more specific error information.

2. Admin Interface and CSS Conflicts

Problem: Recent updates have introduced CSS that affects the entire WordPress admin area, changing background colors and potentially conflicting with other plugins or themes.

Solution:

  • This issue has been addressed in beta versions and will be included in future stable releases. You can try the beta version if this is causing significant interface problems.
  • As a temporary workaround, you can use custom CSS to override the plugin's styles, though this requires technical knowledge of CSS.

3. Performance and Slow Loading Issues

Problem: Some users report the plugin significantly slowing down their site's frontend or backend, with specific functions like PostmanLicenseManager::init taking considerable time to execute.

Solution:

  • Install the Query Monitor plugin to identify exactly which functions are causing performance bottlenecks.
  • Check if the issue is related to external requests (like loading emoji icons from CDNs) that might be timing out.
  • Share your diagnostic report (found in Post SMTP's Troubleshooting section) with the community to help identify patterns in performance issues.

4. Plugin Conflicts

Problem: Post SMTP may conflict with other plugins, particularly those that modify admin capabilities, manage user roles, or handle email functionality.

Solution:

  • If you experience issues with admin menus or capabilities (especially in multisite installations), temporarily disable other admin management plugins to test for conflicts.
  • For conflicts with specific plugins like Adminimize or Backup Buddy, test by deactivating one plugin at a time to identify the source of the conflict.
  • Check the browser console for JavaScript errors that might indicate conflicting scripts.

5. Language and Translation Issues

Problem: The plugin may display in the site's primary language rather than the user's preferred language setting, or show mixed language interfaces.

Solution:

  • Verify your user language setting in your WordPress profile (top right of admin screen).
  • Check for conflicts with multilingual plugins like Polylang, which might be overriding user-specific language settings.
  • Ensure you're using the latest plugin version, as translation handling has been improved in recent updates.

6. Email Log Access Problems

Problem: The Email Log submenu might be missing or inaccessible, particularly on multisite installations or when using custom role management.

Solution:

  • Check your user capabilities - Super Admin status doesn't always guarantee access to all sub-site features in a multisite network.
  • Temporarily disable any user role or capability management plugins to see if they're restricting access to the email log.

General Troubleshooting Steps

For any issue with Post SMTP, follow these basic troubleshooting steps:

  1. Update everything: Ensure WordPress, your theme, and all plugins are updated to their latest versions.
  2. Conflict test: Temporarily switch to a default theme (Twenty Twenty-One) and disable all other plugins to see if the issue persists.
  3. Check diagnostics: Use the Post SMTP diagnostic report (found in the Troubleshooting section) to identify potential configuration issues.
  4. Review error logs: Check your server error logs and WordPress debug log for specific error messages.
  5. Browser console: Check your browser's developer console for JavaScript errors that might indicate frontend issues.

Remember that many issues are environment-specific, so providing detailed information about your setup (PHP version, WordPress version, other active plugins) will help the community provide more targeted assistance. Most issues can be resolved through systematic troubleshooting and keeping the plugin updated to the latest version.

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