You may wish to set up a redirection service.
If you need to send a mail urgently, the Italian Post
(http://www.posteitaliane.it/)
provides a fast mail service (Posta Celere) in most
of the post offices, an warranty to deliver within 24
hours in Italian towns and within 48 hours in the rest
of the country; to send abroad, it takes 24 to 72 hours
in European countries and 3 to 5 days in the rest of
the world.
You can buy stamps in tobacco shops or in post offices.
They are open from 8.30am to 2pm from Monday to Friday
and from 8.30am to 12pm on Saturday. Main post offices
are also open during afternoon.