I'm trying to back up my mail on my webhost by sticking a copy on an
IMAP account. However, whenever I do so, it seems that Outlook 2003
takes the emails with attachments and converts them to winmail.dat
attachments. Also, it sticks a winmail.dat attachment on emails
without attachments. I already know what a winmail.dat file is, I'm
just trying to figure out how to turn off the auto attachment
conversion so that I can use any reader (or none at all) to open these
multi-part attachment emails.

http://www.imap-partners.net/clients.html
"Encoding of MIME attachments
Outlook uses a proprietary format for encoding already-encoded MIME
attachments, namely a file called "winmail.dat" of type
application/ms-tnef. There are various settings in Outlook to override
this, none of which seem to do so reliably, especially when used with
an Exchange server. There are various applications available to
extract the contents, for example Fentun for Windows and linux. A
search for "ms-tnef" and "winmail.dat" will turn up more."

I've tried installing Thunderbird and importing my .pst file from
Outlook 2003, but then I see no attachments! My plan was to use
Thunderbird to stick a copy on my IMAP account. Any suggestions?

Please be aware that these emails are not all encoded with Microsoft's
TNEF winmail.dat system, it's just when I put them on my IMAP account,
it's reconverting them then.

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Clarification of Question by skermit-ga on 18 Oct 2004 12:14 PDT

Oh one more thing, I've already switched the Send format to Plain text
in the Options, it just won't play nice.

skermit-ga

I have a similar issue, 
I have recently upgraded our exchange server from 2000 to 2003. All
users have outlook2003. Some of our customers using outlook express
can not see attached files from some individuals. It's a bit bit wierd
though, if user-A sends customer-A an email with an attachment,
Customer-A recieves the attatchment normally. User-B send the same
email and customer-A cant see any attatchments.
I have a feeling that this is down to the wonderful microsoft protocol
known as TNEF (which no one else will endorse!) Even if User-B sends
the email in plain text there is still a TNEF Correlator value equal
to the Message ID in the Email header, but no attatchment. All the
rigfht ticks have been applied etc...

Is there a way to turn TNEF off in exchange?