Find out from patients whether they prefer to be contacted by text, postcard, email, or phone call. You can also do a combination, i.e., text plus courtesy call, etc.
Note: Older patients still prefer postcards. But as the population ages more patients want a text, and to a lesser degree phone call or email. If you're concerned you won't know if a patient has moved if you stop using postcards, send birthday and holiday cards. That'll keep you in the loop.