Outlook Express

Don't know if I'm in the right forum but Outlook Express
is acting up.
I use Outlook Express as my main e-mail service.
When I send a file it arrives at Hotmail and other freebie
mail services intact, but when I send it to myself at my
Outlook Express address the file arrives with a different
format that can't be opened.
In the "sent items" folder, it has the original format and
opens properly but something strange happens to it when it
arrives in my inbox.
So maybe someone can help me with this or direct me to the
correct forum.
Thanks
Jimbo