Forwarded mail is missing attachment of original mail if using SP2 client.

You received a mail that has a signature including some image file. This mail has also attachment of +2MB size. If you Forward it in a HTML format (not Forward As Attachment) to some Internet recipient, such a mail will not include attachment file of original mail. If you check sent properties of such forwarded mail, you will immediately notice that Mime.822 file listed in attachment section is far smaller in a size than it should be if the attachment would be included in the Mime file.

The problem is caused by having an image file included in the signature of received mail. The same would happen if you have a signature with an image and then someone tries forward your mail.