Add configurable send_as address with envelope fallback

README.md

@@ -49,13 +49,16 @@ First you need to add a new entry to the mail drivers array in your `config/mail
         'address' => env('MAIL_FROM_ADDRESS'),
         'name' => env('MAIL_FROM_NAME'),
     ],
+    'send_as' => env('MAIL_SEND_AS'),
     'save_to_sent_items' =>  env('MAIL_SAVE_TO_SENT_ITEMS', false),
 ],
 ```
 
 For the `client_id`, `client_secret` and `tenant_id` you need to use the values from the Azure App you created in the
 previous step.
 
+The `send_as` option is the email address which is the sender. When left blank then the default sender is used from the `from.address` parameter. To use a different sender the `from.address` (Azure User) must have access to this mailbox.
+
 The `save_to_sent_items` option in Microsoft Graph refers to a parameter that determines whether a sent email should be saved to the sender's "Sent Items" folder within their mailbox. When this option is set to true, the email will be automatically saved to the "Sent Items" folder, providing a record of the communication. Conversely, when it's set to false, the email will not be saved to the "Sent Items" folder.
 
 By default, the save_to_sent_items option is set to false, which means that emails sent through Microsoft Graph won't be saved in the sender's "Sent Items" folder unless explicitly specified otherwise. This behavior can be useful in scenarios where you might want more control over which emails are saved as sent items, perhaps to reduce clutter or ensure confidentiality.

src/MicrosoftGraphTransport.php

@@ -63,7 +63,10 @@ protected function doSend(SentMessage $message): void
             $payload['message']['internetMessageHeaders'] = $headers;
         }
 
-        $this->microsoftGraphApiService->sendMail($envelope->getSender()->getAddress(), $payload);
+        $this->microsoftGraphApiService->sendMail(!empty(config('mail.mailers.microsoft-graph.send_as'))
+            ? config('mail.mailers.microsoft-graph.send_as')
+            : $envelope->getSender()->getAddress(),
+            $payload);
     }
 
     /**