@Lillian61 Well, it is best to keep as much of the communication as possible on the message stream, especially if it's something that could prove contentious in the future and there needs to b a record. Like sending check-in info- a guests could claim you never explained or sent them the door code, when in fact you did.
I guess I got resigned to it back when I started hosting. I need to send my guests a hand-drawn map to my place, as it's impossible to find otherwise. But you can't add attachments to the messages, so I've always had to send it to guests via email.