diff --git a/README.rst b/README.rst
index 58b4189..372802f 100644
--- a/README.rst
+++ b/README.rst
@@ -20,3 +20,14 @@ Here is a configuration example::
    type = radicale_modoboa_auth_oauth2
 
    oauth2_introspection_endpoint = <introspection url>
+
+Alternatively, if you wish to keep the OAuth2 client secret in a seperate file::
+
+   [auth]
+   type = radicale_modoboa_auth_oauth2
+
+   oauth2_introspection_endpoint = <introspection url with no secret/password>
+   oauth2_introspection_endpoint_secret = <path to file containing secret>
+
+Introspection URL may also contain the path to a Unix domain socket for local
+deployments: ``http+unix://radicale@%2Frun%2F<service>%2Fgunicorn.sock/<path>``
diff --git a/radicale_modoboa_auth_oauth2/__init__.py b/radicale_modoboa_auth_oauth2/__init__.py
index 15a999f..c164a8a 100644
--- a/radicale_modoboa_auth_oauth2/__init__.py
+++ b/radicale_modoboa_auth_oauth2/__init__.py
@@ -1,6 +1,7 @@
 """Authentication plugin for Radicale."""
 
-import requests
+import requests_unixsocket
+import urllib3.util  # requests dependency
 
 from radicale.auth.dovecot import Auth as DovecotAuth
 from radicale.log import logger
@@ -18,23 +19,52 @@ class Auth(DovecotAuth):
     [auth]
     type = radicale_modoboa_auth_oauth2
     oauth2_introspection_endpoint = <URL HERE>
+    oauth2_introspection_endpoint_secret = <FILEPATH>  # OPTIONAL: File containing the client secret (if not part of the URL)
     """
 
     def __init__(self, configuration):
         super().__init__(configuration)
         try:
-            self._endpoint = configuration.get("auth", "oauth2_introspection_endpoint")
+            endpoint_url = configuration.get("auth", "oauth2_introspection_endpoint")
         except KeyError:
-            raise RuntimeError("oauth2_introspection_endpoint must be set")
-        logger.warning("Using oauth2 introspection endpoint: %s" % (self._endpoint))
+        	raise RuntimeError("oauth2_introspection_endpoint must be set") from None
+
+        # Optionally read client secret from separate file if not present in URL
+        endpoint_url_dict = urllib3.util.parse_url(endpoint_url)._asdict()
+        auth_parts = endpoint_url_dict["auth"].split(":", 1)
+        if len(auth_parts) == 1:
+            try:
+                secret_path = configuration.get("auth", "oauth2_introspection_endpoint_secret")
+                with open(secret_path) as f:
+                    secret = f.read().rstrip("\r\n")
+            except KeyError:
+                raise RuntimeError(
+                    "oauth2_introspection_endpoint has no client secret and "
+                    "oauth2_introspection_endpoint_secret is not set"
+                ) from None
+            except IOError as exc:
+                raise RuntimeError(
+                    f"Path oauth2_introspection_endpoint_secret ({secret_path}) "
+                    f"could not be read: {type(exc).__name__}: {exc}"
+                ) from exc
+            else:
+                auth_parts.append(secret)
+        del endpoint_url_dict["auth"]
+        self._endpoint = urllib3.util.Url(**endpoint_url_dict).url
+        self._endpoint_auth = tuple(auth_parts)
+
+        # Log OAuth2 introspection URL without secret
+        clean_endpoint_url = urllib3.util.Url(**endpoint_url_dict, auth=f"{auth_parts[0]}:********").url
+        logger.warning(f"Using OAuth2 introspection endpoint: {clean_endpoint_url}")
 
     def _login(self, login, password):
         headers = {"Content-Type": "application/x-www-form-urlencoded"}
         data = {
             "token": password
         }
-        response = requests.post(self._endpoint, data=data, headers=headers)
-        content = response.json()
-        if response.status_code == 200 and content.get("active") and content.get("username") == login:
-            return login
-        return super()._login(login, password)
+        with requests_unixsocket.Session() as session:
+            response = session.post(self._endpoint, data=data, headers=headers, auth=self._endpoint_auth)
+            content = response.json()
+            if response.status_code == 200 and content.get("active") and content.get("username") == login:
+                return login
+            return super()._login(login, password)
diff --git a/requirements.txt b/requirements.txt
index 2e42ba4..445bf44 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,3 @@
 Radicale
 requests
+requests-unixsocket