I forget the details exactly but this is because you have sent a
*non*-plain-text e-mail with an attachment from Outlook and are trying to
read it with a non-Outlook mail client. When you do this Outlook bundles the
whole thing up in a format which only it can read - fine for corporate
Exchange servers but, as you have found out, a pain in the proverbial for
non-Outlook users.
I think you should be able to google for a full explanation but you need to
either:
(a) Use Outlook at home, or
(b) Send the e-mail in Plain Text format