fix: parse .msg uploads via unstructured instead of extract_msg (#26704)

The .msg branch routed to langchain's OutlookMessageLoader, which requires the extract_msg package. extract_msg pins beautifulsoup4<4.14, but we pin unstructured==0.22.31 (needs beautifulsoup4>=4.14.3) and beautifulsoup4==4.14.3, so extract_msg can never be installed alongside the current dependency set. As a result the .msg path could not function on any supported install: uploads failed at runtime with an ImportError, and adding the missing package broke the build with an unsatisfiable resolver error.

Switch to UnstructuredEmailLoader, which parses .msg through unstructured's partition_msg (backed by python-oxmsg). Both are already shipped, so .msg uploads work with no new dependency and no version conflict. Attachment partitioning is disabled to preserve the previous body-only extraction behaviour.

Fixes #26690

backend/open_webui/retrieval/loaders/main.py

@@ -11,7 +11,6 @@ from langchain_community.document_loaders import (
     BSHTMLLoader,
     CSVLoader,
     Docx2txtLoader,
-    OutlookMessageLoader,
     PyPDFLoader,
     TextLoader,
     YoutubeLoader,
@@ -677,7 +676,18 @@ class Loader:
                     )
                     loader = PptxLoader(file_path)
             elif file_ext == 'msg':
-                loader = OutlookMessageLoader(file_path)
+                try:
+                    from langchain_community.document_loaders import (
+                        UnstructuredEmailLoader,
+                    )
+
+                    # unstructured parses .msg via python-oxmsg; avoids extract_msg's beautifulsoup4<4.14 conflict
+                    loader = UnstructuredEmailLoader(file_path, process_attachments=False)
+                except ImportError:
+                    raise ValueError(
+                        "Processing .msg files requires the 'unstructured' package. "
+                        'Install it with: pip install unstructured'
+                    )
             elif file_ext == 'odt':
                 try:
                     from langchain_community.document_loaders import UnstructuredODTLoader