@Jesús-And-Sara0 Although i only use the desktop version,, even that I find to be problematic. I can cut and paste that email address, but if I click on "Email guest" it takes me to taht box you mention, tells me to enter my email address, when I do, it says that address is already on file, but then it doesn't go anywhere.
In any case, I have always written down the guest's phone number and coded email address when I get a booking, which has proven to be invaluable a couple of times when the site was down and I wouldn't have been able to access that information and get in touch with my guest if I didn't have it on paper. As inefficient as you may find it, it takes all of 15 seconds to write that info down. Yes, the coded email address is long-16 numbers and letters, to be exact, but I don't get what you mean about not fully trusting what you write on paper. I write it down, then check to make sure I've copied it correctly. Like I said, it takes all of 15 seconds.