Title: Uncaught Error: Undefined class constant ‘VERSION’ Last modified: April 11, 2021 --- # Uncaught Error: Undefined class constant ‘VERSION’ * Resolved [tlozano](https://wordpress.org/support/users/tlozano/) * (@tlozano) * [5 years, 2 months ago](https://wordpress.org/support/topic/uncaught-error-undefined-class-constant-version/) * First, Thank you for this plugin, it is very good. * I have a problem with “Post SMTP Mailer/Email Log”. It works fine, but if I use“ mailerlite” integration with woocommerce, I get an error and no more emails are sending. Is I use “Mailerlite plugin” without woocommerce integration, it works fine. * This is the error trace in server: [error] FastCGI sent in stderr: “PHP message: PHP Fatal error: Uncaught Error: Undefined class constant ‘VERSION’ in /home/ user/web/xxxx.com/public_html/wp-content/plugins/post-smtp/Postman/Postman-Mail/ google-api-client/vendor/google/apiclient/src/Google/Client.php:1042 Stack trace:# 0 /home/user/web/xxxx.com/public_html/wp-content/plugins/post-smtp/Postman/Postman- Mail/google-api-client/vendor/google/apiclient/src/Google/Client.php(1032): Google_Client- >createDefaultHttpClient() #1 /home/user/web/xxxx.com/public_html/wp-content/ plugins/post-smtp/Postman/Postman-Mail/google-api-client/vendor/google/apiclient/ src/Google/Client.php(356): Google_Client->getHttpClient() #2 /home/user/web/ xxxx.com/public_html/wp-content/plugins/post-smtp/Postman/Postman-Mail/google- api-client/vendor/google/apiclient/src/Google/Client.php(786): Google_Client- >authorize() #3 /home/user/web/xxxx.com/public_html/wp-content/plugins/post-smtp/ Postman/Postman-Mail/google-api-client/vendor/google/apiclient/src/Go” while reading response header from upstream, client: xx.xx.xx.xx, server: xxxx.com, request: “POST / HTTP/1.1”, upstream: “fastcgi://unix:/run/php/php7.4-fpm-xxxx. com.sock:”, host: “xxxx.com”, referrer: “[https://xxxx.com/”](https://xxxx.com/”);` * Any ideas about this error? * Thank you. - This topic was modified 5 years, 2 months ago by [tlozano](https://wordpress.org/support/users/tlozano/). Viewing 3 replies - 1 through 3 (of 3 total) * Thread Starter [tlozano](https://wordpress.org/support/users/tlozano/) * (@tlozano) * [5 years, 2 months ago](https://wordpress.org/support/topic/uncaught-error-undefined-class-constant-version/#post-14308306) * Ok, I have more info. It fails only with Gmail API config. With SMTP config works fine. So, I have disable Gmail API and check SMTP and now it is working fine. * [yehudah](https://wordpress.org/support/users/yehudah/) * (@yehudah) * [5 years, 2 months ago](https://wordpress.org/support/topic/uncaught-error-undefined-class-constant-version/#post-14315773) * Thank you for the update. * [daivatsoni](https://wordpress.org/support/users/daivatsoni/) * (@daivatsoni) * [5 years, 1 month ago](https://wordpress.org/support/topic/uncaught-error-undefined-class-constant-version/#post-14435137) * I am getting the same error with VERSION constant. I found that it conflicts with other plugin “AWS for WordPress” (Amazon Polly) plugin. “GuzzleHttp\ClientInterface” same package is also used in it. What could be the solution? Viewing 3 replies - 1 through 3 (of 3 total) The topic ‘Uncaught Error: Undefined class constant ‘VERSION’’ 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/) * 3 replies * 3 participants * Last reply from: [daivatsoni](https://wordpress.org/support/users/daivatsoni/) * Last activity: [5 years, 1 month ago](https://wordpress.org/support/topic/uncaught-error-undefined-class-constant-version/#post-14435137) * Status: resolved