CardStore Website
I have used a service for years to send out cards and specifically thank you notes to friends. That service shifted their business and discontinued the services that I used. They referred users like me to a new company called cardstore.com. A flat 7×5 card is $1.29. Their customer support told me that they will be coming out with a 4×5 card shortly that will take the postcard postage and be slightly cheaper. What I like about the service is that I am able to send a high quality card to my friends, but not spend any time on production. You might give it a look.