i can scan to email to all user except 1 user, same domain, same network, the email is correct, he can receive from other copier only from the taskalfa 500ci. any ideas??

Safe sender's list?
Does the copier have a legitimate email address or just one that was made up?

If the email address is legit and it is impersonating the user that can't receive the scan it may be due to a filtering technique that assumes any mail labeled from myself that is to myself is bogus and therefore dumped.

I would expect some type of spam filtering is to blame here.

More information is required to really diagnose this. While I understand it's the same domain, who really handles the mail? Is it an internal Exchange server or an external third party service? Is there another means to check the user's mail, like a webmail interface? Does the user in question have a security package that supplements anti-spam - like McAfee or Norton Internet Security?