Well, the truth is I don't know if you'll bring in the "big" client any time soon, but standing on the sidelines won't turn your business around either. OK, you didn't hit a grandslam the last time out; but you certainly didn't strike out. You paid for your printing and picked up some new business. The next time out you might achieve stronger results and even capture the attention of those bigger companies you're targeting. You can try mailing the cards out to the same people, or you may wish to use another list. If you chose the former, the individual who should have received the card in the first place may now actually get your postcard in his hands. There might be follow-up on his end as well and he just might have someone from his office contact you! A new list will provide a whole new playing field. The possibilities are unknown (remember: there is no perfect answer). Yet, the probability that a strong, creative campaign with a memorable targeted message will capture attention, and hopefully clients, is the best attitude to have.
With all marketing we like our clients to do follow-through. You might not be able to call everyone on your mailing list (we can do that for you), but you can do a random sampling. You have the excuse now to make the call and to introduce yourself. You can ask the respondent if he/she received the information and if the answser is positive then you can inquire whether there is a need for your services. If they can't remember your postcard (it might have been included in the trash mail--by mistake, of course) then now's the time to introduce yourself and your company. You can't think of this as cold-calling since you already reached out to the person via your postcard. As a professional, you're simply calling to see if your printed piece was positively received, and if it was, then to try to convert your call into a potential sale.
So whether or not you receive emails or phone calls from your postcard advertising, there are ways to capitalize on the campaign. If you feel strongly about your messge, but come up short with the first mailing, then wait a few weeks and repeat the process. While some might have liked what they saw in your messge but still neglected to respond, maybe this time they will. Reminding others that you're with a great company that does great things is the best approach I can recommend. If they hear and see the message enough times and they like it, chances are they just might pick up the phone and wish to talk.