After activating the O365 plugin, the extra menu appeared under Post SMTP (“Extensions”). Clicking this, showed the page to add my license key. Copied this string from my account page and pushed Activate. Then my site crashed with a fatal error.

The error says “Notice: Undefined index: Class in /xxxxx/wp-content/plugins/post-smtp/Postman/Extensions/License/PostmanLicenseManager.php on line 54”

and also
“Fatal error: Uncaught Error: Class name must be a valid object or a string in /xxxxx/wp-content/plugins/post-smtp/Postman/Extensions/License/PostmanLicenseManager.php:64 Stack trace: #0 /xxxxx/wp-content/plugins/post-smtp/Postman/Postman.php(201): PostmanLicenseManager->init() #1 /xxxxx/wp-includes/class-wp-hook.php(287): Postman->on_plugins_loaded(”) #2 /xxxxx/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array) #3 /xxxxx/wp-includes/plugin.php(484): WP_Hook->do_action(Array) #4 /xxxxx/wp-settings.php(420): do_action(‘plugins_loaded’) #5 /xxxxx/wp-config.php(90): require_once(‘/xxxxx…’) #6 /xxxxx/wp-load.php(37): require_ in /xxxxx/wp-content/plugins/post-smtp/Postman/Extensions/License/PostmanLicenseManager.php on line 64″

Running PHP 7.3, Post SMTP 2.0.21, Office 365 extension: v1.2

Already did a full reinstall of the plugins and even once more with deleting the old variables in my database through phpMyAdmin, to manually delete all Post SMTP settings from the tables.

This happens on two different websites btw. I have both my websites’ URLs added to my profile, so they’re correctly showing in my account here on this page.

(And I’m thinking: could this have something to do with a colliding variable with name Class?)