Spam from me to me

I download emails in two computers. So, I sent me a document, so I can read it later at home.
The message was returned as SPAM !!
Why !?
Sender and Recipient are the same.

The fact that sender and recipient are the same doesn't automatically mark the mail as ham (non-spam). Otherwise all the spammers would send mails using your own e-mail address
It was probably marked as spam based on the content, you should submit the actual message (including all mail headers) to support if there's no good reason for it to be marked as spam. If you forwarded yourself a document on Viagra and Cialis, well..

Nope, it was an MDI document containing a tax related document.

fischermx, as subspace rightly said, it will be good if you can submit this message (along with headers) to us via a ticket.

As a note, Hotmail has always done this to me - if I send an email from my Hotmail to my Hotmail, it puts it into Junk, even though I've added my address into the safe senders. Bizarre!

maybe you two are known spammers

Another note of caution for anyone testing email forwarding: If I send from Gmail to an address that it forwarded to the same Gmail account, it never comes back at all, not even in the spam folder. That really wasted a lot of time once during some testing I think it must be because they are very cautious about loops.

Its different for "accounts" (i.e, alternative "From" addresses) that I have defined in Gmail. If I send to one of them, it comes back immediately without leaving Gmail.

Cheers
Ross