A guest who had a good week at your place is the cheapest booking in the world — and the one most owners pay full price for again, year after year, because they never kept the address.
Check-out is where it is won
People are warm on departure day and distracted three days later. So the work happens on the spot: a card on the kitchen table with your website address rather than your listing name, one sentence ("next time, book directly on the site — it is simpler for everyone"), and the review asked for face to face.
What you may keep
You may keep the e-mail address of a guest who booked with you in order to write to them about similar stays. Three rules that cost nothing: say why you are writing, put a working unsubscribe link in every message, and never sell or pass on the list. Addresses collected from people who never booked need explicit, un-pre-ticked consent.
What to write, and when
Two messages a year beat a monthly newsletter nobody reads. In January, for the summer: the dates still free, one new thing about the place, and an advantage reserved for returning guests. In September, for autumn and the holidays: shoulder season is what regulars accept best, because they already know the place.
The arithmetic
Twenty addresses over a season, one message in January, two week-long bookings at €700: €1,400 with no commission for an hour's work.