All students at Cambridge have an email account, and many choose to list their addresses in the University email directory.
Pigeonholes are numbered at King's, and there is a list of whose pigeonhole is which in the mail room (on the right as you enter the main entrance). Mail can be sent, via the CUSU mail service or by Royal Mail to King's College, Cambridge CB2 1ST. If you do not put the student's box number on, it will be delivered but not as speedily.
The College is concerned about its students' right to privacy, and as a matter of policy does not give out room numbers to non-members of College, so it's best not to try and drop in unannounced. College members may however choose to enter contact details in a book kept in the Porters' Lodge, which is available for visitors.
Contact details for the KCSU (King's College Student Union) and the KCGS (King's College Graduate Society) are on the Departmental contacts page.
Important messages can be phoned to the porters, UK code +44 (0)1223 331100.