I think you need to look at this from their point of view. Petfinder.com gets thousands of new listings every day. I'm sure they don't have time to send emails and ask questions of everyone that posts a listing.

Petfinder.com is an excellent website that is responsible for literally millions of animals finding homes each year. I think it is highly commendable that they screen listings, to screen out breeders, puppy mills, back-yard breeders, etc. That is one of the things that makes them so successful - people can be fairly certain that if they adopt a pet through Petfinder.com, that they are truly helping a homeless animal, not supporting a breeder. IMO, you should be happy they do this, and understand that once in a while they are going to initially screen out someone attempting to post a legitimate ad.

BTW, I'm surprised they let you post at all, unless you have a 501c3 designation, stating that you are a tax-emempt charity. When I set up an account for our local animal shelter on Petfinder.com, I had to provide 501c3 information to them.