This function causes a fetch of the complete, unfiltered RFC2822 format header of the specified message as a text string and returns that text string.
The options are:
FT_UID The msgno argument is a UID
FT_INTERNAL The return string is in "internal" format,
without any attempt to canonicalize to CRLF
newlines
FT_PREFETCHTEXT The RFC822.TEXT should be pre-fetched at the
same time. This avoids an extra RTT on an
IMAP connection if a full message text is
desired (e.g. in a "save to local file"
operation)