diff --git a/pyas2lib/as2.py b/pyas2lib/as2.py
index 9c74e54..e65c288 100644
--- a/pyas2lib/as2.py
+++ b/pyas2lib/as2.py
@@ -564,7 +564,14 @@ def _decompress_data(self, payload):
 
         return False, payload
 
-    def parse(self, raw_content, find_org_cb, find_partner_cb, find_message_cb=None):
+    def parse(
+        self,
+        raw_content,
+        find_org_cb=None,
+        find_partner_cb=None,
+        find_message_cb=None,
+        find_org_partner_cb=None,
+    ):
         """Function parses the RAW AS2 message; decrypts, verifies and
         decompresses it and extracts the payload.
 
@@ -572,18 +579,24 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, find_message_cb=None)
             A byte string of the received HTTP headers followed by the body.
 
         :param find_org_cb:
-            A callback the returns an Organization object if exists. The
+            A conditional callback the returns an Organization object if exists. The
             as2-to header value is passed as an argument to it.
 
         :param find_partner_cb:
-            A callback the returns an Partner object if exists. The
+            A conditional callback the returns a Partner object if exists. The
             as2-from header value is passed as an argument to it.
 
         :param find_message_cb:
-            An optional callback the returns an Message object if exists in
+            An  optional callback the returns a Message object if exists in
             order to check for duplicates. The message id and partner id is
             passed as arguments to it.
 
+        :param find_org_partner_cb:
+            A conditional callback that return Organization object and
+            Partner object if exist. The as2-to and as2-from header value
+            are passed as an argument to it. Must be provided
+            when find_org_cb and find_org_partner_cb is None.
+
         :return:
             A three element tuple containing (status, (exception, traceback)
             , mdn). The status is a string indicating the status of the
@@ -592,6 +605,18 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, find_message_cb=None)
             the partner did not request it.
         """
 
+        # Validate passed arguments
+        if not any(
+            [
+                find_org_cb and find_partner_cb and not find_org_partner_cb,
+                find_org_partner_cb and not find_partner_cb and not find_org_cb,
+            ]
+        ):
+            raise TypeError(
+                "Incorrect arguments passed: either find_org_cb and find_partner_cb "
+                "or only find_org_partner_cb must be passed."
+            )
+
         # Parse the raw MIME message and extract its content and headers
         status, detailed_status, exception, mdn = "processed", None, (None, None), None
         self.payload = parse_mime(raw_content)
@@ -605,14 +630,17 @@ def parse(self, raw_content, find_org_cb, find_partner_cb, find_message_cb=None)
         try:
             # Get the organization and partner for this transmission
             org_id = unquote_as2name(as2_headers["as2-to"])
-            self.receiver = find_org_cb(org_id)
-            if not self.receiver:
-                raise PartnerNotFound(f"Unknown AS2 organization with id {org_id}")
-
             partner_id = unquote_as2name(as2_headers["as2-from"])
-            self.sender = find_partner_cb(partner_id)
-            if not self.sender:
-                raise PartnerNotFound(f"Unknown AS2 partner with id {partner_id}")
+            if find_org_partner_cb:
+                self.receiver, self.sender = find_org_partner_cb(org_id, partner_id)
+            elif find_org_cb and find_partner_cb:
+                self.receiver = find_org_cb(org_id)
+                if not self.receiver:
+                    raise PartnerNotFound(f"Unknown AS2 organization with id {org_id}")
+
+                self.sender = find_partner_cb(partner_id)
+                if not self.sender:
+                    raise PartnerNotFound(f"Unknown AS2 partner with id {partner_id}")
 
             if find_message_cb and find_message_cb(self.message_id, partner_id):
                 raise DuplicateDocument(
diff --git a/pyas2lib/tests/test_basic.py b/pyas2lib/tests/test_basic.py
index fed94b9..87f09cb 100644
--- a/pyas2lib/tests/test_basic.py
+++ b/pyas2lib/tests/test_basic.py
@@ -184,6 +184,30 @@ def test_encrypted_signed_compressed_message(self):
         self.assertEqual(out_message.mic, in_message.mic)
         self.assertEqual(self.test_data.splitlines(), in_message.content.splitlines())
 
+    def test_encrypted_signed_message_partnership(self):
+        """Test Encrypted Signed Uncompressed Message with Partnership"""
+
+        # Build an As2 message to be transmitted to partner
+        self.partner.sign = True
+        self.partner.encrypt = True
+        out_message = as2.Message(self.org, self.partner)
+        out_message.build(self.test_data)
+        raw_out_message = out_message.headers_str + b"\r\n" + out_message.content
+
+        # Parse the generated AS2 message as the partner
+        in_message = as2.Message()
+        status, _, _ = in_message.parse(
+            raw_out_message,
+            find_org_partner_cb=self.find_org_partner,
+        )
+
+        # Compare the mic contents of the input and output messages
+        self.assertEqual(status, "processed")
+        self.assertTrue(in_message.signed)
+        self.assertTrue(in_message.encrypted)
+        self.assertEqual(out_message.mic, in_message.mic)
+        self.assertEqual(self.test_data.splitlines(), in_message.content.splitlines())
+
     def test_plain_message_with_domain(self):
         """Test Message building with an org domain"""
 
@@ -229,3 +253,6 @@ def find_org(self, as2_id):
 
     def find_partner(self, as2_id):
         return self.partner
+
+    def find_org_partner(self, as2_org, as2_partner):
+        return self.org, self.partner