This was policy worked on my Austin or San Antonio Money Mailer sales teams:

If you left the meeting having welcomed your newest client on board, be sure to complete the client’s great initial experience by sending a Thank You Card immediately. If the prospect did not make a decision in the appointment or decided “no,” send a card thanking the prospect for their time. A little courtesy and appreciation goes a long way. It really stands out in today’s “WIIFM” business culture. Sending thanks to prospects could greatly increase their chances of eventually becoming clients.

It has been my personal policy for years. Many of the Account Executives commented on positive feedback they got from prospects and clients. An attitude of gratitude is good for a person, and good for sales!