I'm a developer working on a Python project called "msg extractor" that is able to open and understand a good portion of the .msg file format, the format the Outlook saves messages in. While trying to expand it's capabilities, I came across a specific type of attachment only noted in the documentation I could find as being in "Application specific format" (Property PidTagAttachMethod, value afStorage). While I can't reasonably add support for formats from every singly email program, I would like to be able to add support for any attachments that Outlook might create. As such, I was wondering if documentation on the types of attachments Outlook creates has been published anywhere?
The specific attachment that I keep finding has to do with having a signature that contains an image.