diff --git a/modoboa/webmail/lib/sendmail.py b/modoboa/webmail/lib/sendmail.py
index 300646d0c..7635657e9 100644
--- a/modoboa/webmail/lib/sendmail.py
+++ b/modoboa/webmail/lib/sendmail.py
@@ -96,12 +96,13 @@ def schedule_email(
         mattachment = models.MessageAttachment(
             message=sched_msg,
         )
-        if "content-type" in attachment:
-            mattachment.content_type = attachment["content-type"]
-        elif "Content-Type" in attachment:
-            mattachment.content_type = attachment["Content-Type"]
-        else:
+        for header in ["content-type", "Content-Type"]:
+            if header in attachment:
+                mattachment.content_type = attachment[header]
+                break
+        if not mattachment.content_type:
             continue
+
         mattachment.file.name = attachment["tmpname"]
         if "fname" in attachment:
             mattachment.filename = attachment["fname"]
diff --git a/modoboa/webmail/tests/test_viewsets.py b/modoboa/webmail/tests/test_viewsets.py
index 6801256cf..f4c6febfd 100644
--- a/modoboa/webmail/tests/test_viewsets.py
+++ b/modoboa/webmail/tests/test_viewsets.py
@@ -419,6 +419,7 @@ class ComposeSessionViewSetTestCase(WebmailTestCase):
                 {
                     "sender": self.user.email,
                     "to": ["test@example.test"],
+                    "cc": ["cc@example.test"],
                     "subject": "test",
                     "body": "Test",
                     "scheduled_datetime": scheduled_datetime.isoformat(),