diff --git a/app/__init__.py b/app/__init__.py
index 1f68d0f5..cc09b792 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -12,7 +12,7 @@ from logging.handlers import SMTPHandler, WatchedFileHandler
 
 from flask import current_app, g, request
 from flask import Flask
-from flask import abort, has_request_context
+from flask import abort, has_request_context, jsonify
 from flask import render_template
 from flask.logging import default_handler
 from flask_sqlalchemy import SQLAlchemy
@@ -24,7 +24,7 @@ from flask_moment import Moment
 from flask_caching import Cache
 import sqlalchemy
 
-from app.scodoc.sco_exceptions import ScoValueError
+from app.scodoc.sco_exceptions import ScoValueError, APIInvalidParams
 from config import DevConfig
 import sco_version
 
@@ -56,6 +56,12 @@ def internal_server_error(e):
     return render_template("error_500.html", SCOVERSION=sco_version.SCOVERSION), 500
 
 
+def handle_invalid_usage(error):
+    response = jsonify(error.to_dict())
+    response.status_code = error.status_code
+    return response
+
+
 def render_raw_html(template_filename: str, **args) -> str:
     """Load and render an HTML file _without_ using Flask
     Necessary for 503 error mesage, when DB is down and Flask may be broken.
@@ -94,13 +100,8 @@ class ScoSMTPHandler(SMTPHandler):
     def getSubject(self, record: logging.LogRecord) -> str:
         stack_summary = traceback.extract_tb(record.exc_info[2])
         frame_summary = stack_summary[-1]
-        subject = f"Sco Exc: {record.exc_info[0].__name__} in {frame_summary.name} {frame_summary.filename}"
-        # stack_summary.reverse()
-        # with open("/tmp/looooo", "wt") as f:
-        #     for frame_summary in stack_summary:
-        #         f.write(
-        #             f"{record.exc_info[0].__name__} in {frame_summary.name} {frame_summary.filename}\n"
-        #         )
+        subject = f"ScoExc({sco_version.SCOVERSION}): {record.exc_info[0].__name__} in {frame_summary.name} {frame_summary.filename}"
+
         return subject
 
 
@@ -121,6 +122,7 @@ def create_app(config_class=DevConfig):
     app.register_error_handler(ScoValueError, handle_sco_value_error)
     app.register_error_handler(500, internal_server_error)
     app.register_error_handler(503, postgresql_server_error)
+    app.register_error_handler(APIInvalidParams, handle_invalid_usage)
 
     from app.auth import bp as auth_bp
 
@@ -168,7 +170,6 @@ def create_app(config_class=DevConfig):
                     mailhost=(app.config["MAIL_SERVER"], app.config["MAIL_PORT"]),
                     fromaddr="no-reply@" + app.config["MAIL_SERVER"],
                     toaddrs=["exception@scodoc.org"],
-                    subject="ScoDoc Exception from " + host_name,
                     credentials=auth,
                     secure=secure,
                 )
diff --git a/app/scodoc/sco_exceptions.py b/app/scodoc/sco_exceptions.py
index 12aa05a1..5ae9ace4 100644
--- a/app/scodoc/sco_exceptions.py
+++ b/app/scodoc/sco_exceptions.py
@@ -96,3 +96,20 @@ class ScoGenError(ScoException):
 
 class ScoInvalidDateError(ScoValueError):
     pass
+
+
+# Pour les API JSON
+class APIInvalidParams(Exception):
+    status_code = 400
+
+    def __init__(self, message, status_code=None, payload=None):
+        Exception.__init__(self)
+        self.message = message
+        if status_code is not None:
+            self.status_code = status_code
+        self.payload = payload
+
+    def to_dict(self):
+        rv = dict(self.payload or ())
+        rv["message"] = self.message
+        return rv