The O365 Extension worked well, that’s nothing to do with tokens, connection with outlook API… in fact, the plugin is sending mails correctly!
But if for instance I edit an order (change status) it gives error 500.
When I enable debug and repeat the same “quick order edit” on orders page, it shows the following error (I even don’t know why this error is showing up here, on orders page, as this plugin has nothing to do on this case…)
Error (first domain folder ommited from urls for privacy):
Fatal error: Uncaught Error: Call to undefined function GuzzleHttp\choose_handler() in wp-content/plugins/post-smtp-extension-office365/vendor/guzzlehttp/guzzle/src/HandlerStack.php:40 Stack trace: #0 wp-content/plugins/post-smtp-extension-office365/vendor/guzzlehttp/guzzle/src/Client.php(65): GuzzleHttp\HandlerStack::create() #1 wp-content/plugins/post-smtp-extension-office365/vendor/league/oauth2-client/src/Provider/AbstractProvider.php(132): GuzzleHttp\Client->__construct(Array) #2 wp-content/plugins/post-smtp-extension-office365/vendor/league/oauth2-client/src/Provider/GenericProvider.php(99): League\OAuth2\Client\Provider\AbstractProvider->__construct(Array, Array) #3 wp-content/plugins/post-smtp-extension-office365/inc/TokenCache.php(64): League\OAuth2\Client\Provider\GenericProvider->__construct(Array) #4 wp-content/plugins/post-smtp-extension-office365/inc/Engine.php(88): Office365PostSMTP\ in wp-content/plugins/post-smtp-extension-office365/vendor/guzzlehttp/guzzle/src/HandlerStack.php on line 40
Seems some problem with Guzzle library, I have seen some reports with other plugins having the same error.
I also tried to find a new version of the o365 extension, just in case you updated it, but I found the extension is retired ¿?