@girish My initial question was related to fact that per app password follow the same dynamic of SFTP. Each SFTP have ability to have his own password, so I was sure also each email have his own password.
I think this part can be improved. Eg, giving ability to use single specific password each mailbox. This is useful also to improve security. In fact, if someone spoof password eg. on public wifi on single email, he can access also all other emails.
Hope I was clear. Thank's!