Lee White says a little bit about this in one of the threads. I'll copy and paste it for you so you don't have to go search for it.
"....... Postcard campaigns are awesome, especially in the digital age. People like receiving something in the mail. It also shows you are a professional because it aint cheap! It shows you are serious.
I recommend using a mailing list company like Adbase http://www.adbase.com/ (unless you have an agent that may have a better list). Adbase is expensive, but there really isn't any better way to get a huge list of client addresses that are current. Trying to do it on your own is overwhelming. Also, the people in the industry move around so much you would never be able to keep track of them.
Like I mentioned before, plan a whole campaign. A single mailing is useless and many people give up after one or two mailings. Think about it this way, how many times do big companies hit you with their ads? Over and over right! They know it takes a certain amount of exposure to have something sink in. Unfortunately illustrators think that when they send a postcard it's going to stop the presses and you will be "the next BIG thing"! I wish it worked that way, but it takes time just like advertising does for any business.
On top of postcards, I suggest a small (20 clients or less) targeted mailing that is custom and a bit fancier than a postcard. I sent a handmade book to 21 potential clients and actually got 13 face to face meetings with them. A few I ended up working with right away. One of them took 10 years to call me, but eventually the call came! Like I said, it's a marathon and not a sprint so plan accordingly.
The response rate of a GOOD postcard is around 2%, so if you send out 1000, you can expect maybe 20 people to actually visit your website. Once clients get used to seeing your name on the postcards, the rate goes up and is much more effective. Typically people see results after sending 5-6 postcards, so it really is a long slow burn. I can talk more about this if people are interested..."
