Add custom headers to email

O365/message.py

@@ -340,7 +340,7 @@ def __init__(self, *, parent=None, con=None, **kwargs):
         self.web_link = cloud_data.get(cc('webLink'), '')
 
         # Headers only retrieved when selecting 'internetMessageHeaders'
-        self.message_headers = cloud_data.get(cc('internetMessageHeaders'), [])
+        self.__message_headers = cloud_data.get(cc('internetMessageHeaders'), [])
 
     def __str__(self):
         return self.__repr__()
@@ -622,6 +622,31 @@ def single_value_extended_properties(self):
         """ singleValueExtendedProperties """
         return self.__single_value_extended_properties
 
+    @property
+    def message_headers(self):
+        """ Custom message headers
+            List of internetMessageHeaders, see definition: https://learn.microsoft.com/en-us/graph/api/resources/internetmessageheader?view=graph-rest-1.0
+        :type: list[dict[str, str]]
+        """
+
+        return self.__message_headers
+
+    @message_headers.setter
+    def message_headers(self, value):
+        if not isinstance(value, list):
+            raise ValueError('"message_header" must be a list')
+
+        self.__message_headers = value
+        self._track_changes.add('message_headers')
+
+    def add_message_header(self, name, value):
+        # Look if we already have the key. If we do, update it, otherwise write
+        for header in self.__message_headers:
+            if header["name"] == name:
+                header["value"] = value
+                return
+        self.__message_headers.append({"name": name, "value": value})
+
     def to_api_data(self, restrict_keys=None):
         """ Returns a dict representation of this message prepared to be sent
         to the cloud
@@ -686,6 +711,9 @@ def to_api_data(self, restrict_keys=None):
             # this property does not form part of the message itself
             message[cc('parentFolderId')] = self.folder_id
 
+        if self.message_headers:
+            message[cc('internetMessageHeaders')] = self.message_headers
+
         if restrict_keys:
             for key in list(message.keys()):
                 if key not in restrict_keys:

tests/test_message.py

@@ -211,6 +211,25 @@ def test_save_draft_with_with_large_attachment_when_object_id_is_set(self):
         assert msg.con.calls[2].payload == b"conte"
         assert msg.con.calls[3].payload == b"nt"
 
+    def test_save_draft_with_custom_header(self):
+        msg = message()
+        msg.subject = "Test"
+        my_custom_header = [{"name": "x-my-custom-header", "value": "myHeaderValue"}]
+        msg.message_headers = my_custom_header
+
+        assert msg.save_draft() is True
+        [call] = msg.con.calls
+        assert call.url == self.base_url + "me/mailFolders/Drafts/messages"
+        assert call.payload == {
+            "body": {"content": "", "contentType": "HTML"},
+            "flag": {"flagStatus": "notFlagged"},
+            "importance": "normal",
+            "isDeliveryReceiptRequested": False,
+            "isReadReceiptRequested": False,
+            "subject": "Test",
+            "internetMessageHeaders": my_custom_header,
+        }
+
     def test_save_message(self):
         msg = message(__cloud_data__={"id": "123", "isDraft": False})
         msg.subject = "Changed"
@@ -291,6 +310,25 @@ def test_send(self):
             "saveToSentItems": False,
         }
 
+    def test_send_with_headers(self):
+        my_testheader = {"x-my-custom-header": "some_value"}
+        msg = message(__cloud_data__={"internetMessageHeaders": [my_testheader]})
+        assert msg.send(save_to_sent_folder=False)
+        [call] = msg.con.calls
+        assert call.url == self.base_url + "me/sendMail"
+        assert call.payload == {
+            "message": {
+                "body": {"content": "", "contentType": "HTML"},
+                "flag": {"flagStatus": "notFlagged"},
+                "importance": "normal",
+                "isDeliveryReceiptRequested": False,
+                "isReadReceiptRequested": False,
+                "subject": "",
+                "internetMessageHeaders": [my_testheader],
+            },
+            "saveToSentItems": False,
+        }
+
     def test_send_existing_object(self):
         msg = message(__cloud_data__={"id": "123"})
         assert msg.send()