For communicating Politecnico will use only your institutional e-mail, assigned at first enrolment. The formula is: s<studentnumber>@studenti.polito.it
Those account will be valid even after graduating or leaving. 
No other addresses will be taken into consideration. 
 
For info at the Registrar’s Office desks, the student can delegate a trusted person, signing a proxy and giving an identity document photocopy.