It's a multi-part mime file.
OK, This is going to be a bit longwinded but stick with me!
Attachments cannot be posted to newsgroups or sent out in email. So how is it done?
The email software converts the attachment into a text equivalent - Therefore any attachment (mpg, jpg, etc) will look like your example above.
At the other end the email software pieces it back together and you get your attachment non the wiser that this process has occured.
Now, With newsgroups, certain groups have a limit on what can be posted.
So, If you post a large picture file that is to big for a single posting you split it into a multi-part posting.
Quite often, These posts have things like [1/5] on the end.
What you need to do is get all the parts together and then OE should be able to assemble your attachment.
Hope that helps!
Gary.