Your Site is Experiencing a Technical Issue Error

Hi, I started getting WordPress “Your Site is Experiencing a Technical Issue” emails for this plugin. It seems to be working okay, do you know what might be causing this?

Thanks!

Error Details
=============
An error of type E_ERROR was caused in line 329 of the file /home/conexo/public_html/wp-content/plugins/post-smtp/Postman/Postman-Mail/PostmanSmtpModuleTransport.php. Error message: Uncaught Error: Class ‘PostmanAdminController’ not found in /home/conexo/public_html/wp-content/plugins/post-smtp/Postman/Postman-Mail/PostmanSmtpModuleTransport.php:329

Stack trace:
#0 /home/conexo/public_html/wp-content/plugins/post-smtp/Postman/Postman-Mail/PostmanSmtpModuleTransport.php(294): PostmanSmtpModuleTransport->addSettings()
#1 /home/conexo/public_html/wp-includes/class-wp-hook.php(287): PostmanSmtpModuleTransport->on_admin_init(”)
#2 /home/conexo/public_html/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array)
#3 /home/conexo/public_html/wp-includes/plugin.php(478): WP_Hook->do_action(Array)
#4 /home/conexo/public_html/wp-content/plugins/iwp-client/core.class.php(250): do_action(‘admin_init’)
#5 /home/conexo/public_html/wp-includes/class-wp-hook.php(287): IWP_MMB_Core->admin_wp_loaded_iwp(”)
#6 /home/conexo/public_html/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array)
#7 /home/conexo/public_html/wp-includes/plugin.php(478): WP_Hook->do_action(Array)
#8
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