If you email them a code, odds are that they need to open their phone anyway to see the code. Which is more of a hastle than just using the phone. [Scrolling through messages or Emails on phone]. You're on vacation seeing different things, navigating a new town, embracing new experiences, odds are you won't remember a random code.
I have seen people using the last 4 digits of the Guest's phone number. I think there's some danger in that (if other people know your "method" of code generation), but the rest of the traveling party still has to check their phone to remember the code. Confession: I don't know the actual numbers of even my best friends, I just have them as a contact.
If the guest is "old school" and has the print out of the reservation & the door code on them... Better hope they don't lose it or get it stolen, because now a violator has full access to your property.
Phones do offer huge advantages in security. For one, you can have a log of who opened the deadbolt. If there was a robbery (actual or fruad), there is the ability to see that a staff member entered their room & may be the culprit. There is also the ability to ensure that the cleaning staff only has access from 11a-3p on specific days, so that you're not wondering if they entered the combination to commit the crime. Wouldn't it be nice to end the investigation immediately by showing airbnb, "No one else entered the property, here is the log. This is clearly a fraud attempt."
I don't think **all guests want** any one type of entry. Whether it's to:
- carry a key,
- use a key card,
- remember and use a code, or
- use an app
The question is which method is the most safe, secure, and convenient for your property & your situation?