Here, there and everywhere

My dad (from Estonia) went away to the States, to visit my brother who's studying there. Before leaving, he wrote me a note saying "keep me up to date, I'll be staying with our relatvies, their e-mail is something@hotmail.com". And then it struck me - he normally uses hot.ee which is like Estonian Hotmail. Why would I need to write to a different address while he's abroad?