This is one of those two-way blame games, each side saying its the other's fault. Take a look as MSKB articles Q136204 and Q138053. They expain this pretty well. In a nutshell, the MS mail client sends out the message as rich text, assuming the recipient can also receive rich-text (and of course, since nobody uses anything but Microsoft soaftware, this is a safe assumption, right?). Unfortunately, Notes decides all that rich-text stuff isn't purely SMTP compliant, so it's turned into an attachment, which you then have no way of opening unless you install a MS mail program (i.e. Outlook or Outlook Express). I'm sure there must be a utility out there that'll let you open the .dtf without installing a MS mail app, but I haven't come across one yet. Short term, the best you can do is ask the sender to open your address in their address book, go to the "SMTP Address" tab and turn off the "Always Send to this Recipient in Microsoft Exchange Rich Text Format" option.
