The Application Process

I realize having my recommenders mention the school by name in each recommendation letter is best, but would it be frowned upon by adcoms if the recommendation letters were simply addressed as "To Whom it May Concern," with no mention of the school's name?

I ask because I am coaching my recommenders from abroad and there is a 13 hour time difference, making it more difficult to coordinate with their already busy schedules.

Many thanks in advance!