Fix missing subject on emails with attachments

- Ensure Subject header is set on the outermost MIME part when attachments are present
- Restructure send_email to use multipart/mixed as root with headers when attachments exist

scraibe/email_sender.py

@@ -223,27 +223,27 @@ def send_email(
 
     subject = subject.strip()
 
-    # Build message
-    msg = MIMEMultipart("alternative")
+    has_attachments = bool(attachments)
+
+    # Build the text/HTML part (alternative)
+    alt = MIMEMultipart("alternative")
+    alt.attach(MIMEText(body, "plain"))
+    if html:
+        alt.attach(MIMEText(html, "html"))
+
+    if has_attachments:
+        # Outer message: multipart/mixed with headers
+        msg = MIMEMultipart("mixed")
         msg["From"] = cfg["from_address"]
         msg["To"] = ", ".join(to_list)
         if cc_list:
             msg["Cc"] = ", ".join(cc_list)
         msg["Subject"] = subject
 
-    # Attach plain text
-    msg.attach(MIMEText(body, "plain"))
-
-    # Attach HTML if provided
-    if html:
-        msg.attach(MIMEText(html, "html"))
-
-    # Attach files in a separate multipart/mixed part
-    if attachments:
-        mixed = MIMEMultipart("mixed")
-        mixed.attach(msg)
-        msg = mixed
+        # Attach the alternative (text/HTML) part
+        msg.attach(alt)
 
+        # Attach files
         for file_path in attachments:
             if not os.path.isfile(file_path):
                 logger.warning("Attachment file not found, skipping: %s", file_path)
@@ -262,6 +262,14 @@ def send_email(
                     msg.attach(part)
             except Exception as e:
                 logger.warning("Failed to attach file %s: %s", file_path, e)
+    else:
+        # No attachments: use the alternative part as the root message
+        msg = alt
+        msg["From"] = cfg["from_address"]
+        msg["To"] = ", ".join(to_list)
+        if cc_list:
+            msg["Cc"] = ", ".join(cc_list)
+        msg["Subject"] = subject
 
     # Connect and send
     try: