mimepart:FileData(file$)
file$. This is an alternative
to using mimepart:Data(). As a side effect, the part's remote file name is set to the base name
of the given filename if it is a valid named file. This can be undone or overridden by a subsequent call
to mimepart:Filename().
The contents of the file is read during the file transfer in a streaming manner to allow huge files to get transferred without using much memory. It therefore requires that the file is kept intact during the entire request.
If the file size cannot be determined before actually reading it (such as for a device or named pipe), the whole mime structure containing the part will be transferred as chunks by HTTP and rejected by IMAP.
Mime parts are created using mime:AddPart().