# Subfile Extraction

To convert a file, you must first determine whether the source file contains any subfiles (attachments, embedded objects, and so on). A file that contains subfiles is called a container file. Compressed files (such as Zip), mail messages with attachments (such as Microsoft Outlook Express), mail stores (such as Microsoft Outlook Personal Folders), and compound documents with embedded OLE objects (such as a Microsoft Word document with an embedded Excel chart) are examples of container files.

If the file is a container file, the container must be opened and its subfiles extracted by using the File Extraction API. The extraction process is done repeatedly until all subfiles are extracted and exposed for conversion. After a subfile is extracted, you can use the HTML Export API to convert the file.

If a file is not a container, you should pass it directly to the HTML Export API for conversion without extraction.

See Use the File Extraction API for more information.

## Convert Outlook Email without Using the Extraction API

Micro Focus strongly recommends that you convert all container files, including Microsoft Outlook files, by using the File Extraction API. However, you can convert Outlook email messages (MSG) directly by using the Export API and the MSG reader (msgsr).

NOTE: The MSG reader only extracts the message body of an MSG file. Attachments are not extracted.

To convert MSG files by using the MSG reader, add the following to the `formats_e.ini` file (`TRUE` is case-sensitive):

    [ContainerOptions]
    bConvertMSG=TRUE

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