Title: Error when using another custom plugin
Last modified: January 14, 2023

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# Error when using another custom plugin

 *  Resolved [Cindy Cullen](https://wordpress.org/support/users/cgcullen/)
 * (@cgcullen)
 * [3 years, 2 months ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/)
 * I am getting this error:
 * Fatal error: Uncaught Error: Call to undefined function PostSMTP\Vendor\GuzzleHttp\
   choose_handler()
   in /wp-content/plugins/post-smtp/Postman/Postman-Mail/libs/vendor_prefixed/
   guzzlehttp/guzzle/src/HandlerStack.php on line 39

Viewing 6 replies - 1 through 6 (of 6 total)

 *  Plugin Support [M Haseeb](https://wordpress.org/support/users/haseeb0001/)
 * (@haseeb0001)
 * [3 years, 2 months ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/#post-16374802)
 * [@cgcullen](https://wordpress.org/support/users/cgcullen/) Hi,
 * I hope you are doing well.
 * Let me know which mailing service you are using with Post SMTP ?
 * Share the Screenshot of the error and, if possible, share Post SMTP diagnostic
   test report.
 * Thanks
 *  Thread Starter [Cindy Cullen](https://wordpress.org/support/users/cgcullen/)
 * (@cgcullen)
 * [3 years, 2 months ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/#post-16374822)
 * I am using gmail for the mailing service.
 * Sending a test email works. Most emails work. It’s only when I use one plugin
   that sends a notification that I get the error. The plugin is a custom built 
   plugin and I’m trying to get more info from the author as to how they are sending
   the notification.
 * ![](https://i0.wp.com/cullenwebservices.com/error.jpg?ssl=1)
 *  Plugin Support [M Haseeb](https://wordpress.org/support/users/haseeb0001/)
 * (@haseeb0001)
 * [3 years, 2 months ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/#post-16377390)
 * Hi [@cgcullen](https://wordpress.org/support/users/cgcullen/)
 * Please share the plugin name which is conflicting with Post SMTP.
 * Share the Diagnostic Test Report of Post SMTP.
 * Share the Use case of this error so then we can reproduce this on our staging
   websites.
 * Thanks
 *  Plugin Support [M Haseeb](https://wordpress.org/support/users/haseeb0001/)
 * (@haseeb0001)
 * [3 years ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/#post-16564615)
 * Hi [@cgcullen](https://wordpress.org/support/users/cgcullen/) ,
 * Hope you are doing good. We have been waiting to hear from you for the last four
   weeks and assume your issue has been resolved.
 * Feel free to reopen this issue in case the problem persists.
 * Thanks and regards,
   Support Team – WPExperts
 *  Thread Starter [Cindy Cullen](https://wordpress.org/support/users/cgcullen/)
 * (@cgcullen)
 * [3 years ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/#post-16565359)
 * It was a custom plugin. The other plugin author made a work around for the issue.
 *  Plugin Support [M Haseeb](https://wordpress.org/support/users/haseeb0001/)
 * (@haseeb0001)
 * [3 years ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/#post-16568299)
 * [@cgcullen](https://wordpress.org/support/users/cgcullen/) glad to hear that 
   your issue is resolved now.
 * Do let us know if there is any thing we can help you with.
 * Thanks and regards,
   Support Team – WPExperts

Viewing 6 replies - 1 through 6 (of 6 total)

The topic ‘Error when using another custom plugin’ is closed to new replies.

 * ![](https://ps.w.org/post-smtp/assets/icon-128x128.gif?rev=3209655)
 * [Post SMTP – Complete Email Deliverability and SMTP Solution with Email Logs, Alerts, Backup SMTP & Mobile App](https://wordpress.org/plugins/post-smtp/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/post-smtp/#faq)
 * [Support Threads](https://wordpress.org/support/plugin/post-smtp/)
 * [Active Topics](https://wordpress.org/support/plugin/post-smtp/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/post-smtp/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/post-smtp/reviews/)

 * 6 replies
 * 2 participants
 * Last reply from: [M Haseeb](https://wordpress.org/support/users/haseeb0001/)
 * Last activity: [3 years ago](https://wordpress.org/support/topic/error-when-using-another-custom-plugin/#post-16568299)
 * Status: resolved