This method opens the specified file, reads the contents into
memory and then parses the message. The file must be a text file
which uses the standard MIME message structure. It may contain
multiple parts, including file attachments and alternative
representations of the same message. This function cannot be used to
open messages stored in a binary format.
The maximum size of an individual message is 2 GiB (approximately 2
billion characters). This limitation is implemented as a safety check
to prevent opening very large files which are unlikely to contain a
valid MIME formatted message. Most services impose much lower limits
on the maximum size of an individual mail message.
Note: This method can only be used to open and parse
messages structured according to the MIME (Multipurpose Internet
Mail Extensions) standard, such as plain text .eml
or .txt files. It cannot open messages stored in
proprietary or binary formats used by certain email clients. For
example, it does not support Microsoft Outlook message files such
as .msg or mailbox files like .pst and
.ost, nor does it support formats used by other
clients such as Thunderbird's .msf (mail summary files)
or the mbox family (.mbx, .mbox) when
stored as binary containers. Attempting to open these file types
will result in an error. If you need to work with messages exported
from Outlook or other proprietary clients, first save or export
them in the standard text format before using this method.
If another message was previously opened or created using the same
instance of the control, the internal handle which references the previous
message will be closed. If you wish to preserve any changes made to
the current message, use the Export method prior to
calling this method.