@Ivan657 There is no requirement for a guest to use anything other than the Airbnb messaging system, so if you don't feel comfortable with it, tell that to the host and insist that he stick to that for your booking. If he refuses, or says it's not possible, contact Airbnb for their opinion and suggestions. They may contact the host and read him the riot act. If he wants guests to use that other site, he needs to make that clear in his listing info so it's clear before you book.