I've never really used the Junk Email option, but I don't think it would
help much as you would have to add each new sender to the junk list, and its
probably quite likely that most of your junk messages would be from
different senders.
I would use rules:
Rule 1
Check messages when they arrive, from certain contacts (select your hotmail
and yahoo contacts), stop processing rules. (You could have them moved etc,
but finish with stop proccessing rules.
Rule 2
Check messages when they arrive, with specific words in the senders address
(hotmail.com), delete/move etc.
Rule 3
Check messages when they arrive, with specific words in the senders address
(yahoo.com), delete/move etc.
Simon