Dear Miss Snark,
If you don't have publishing credits is it a minus, or rather, is it a plus if you do?
If you've received flattering rejection notes from, say, The New Yorker and Esquire is it worth mentioning? Or, is that worse than having no pub credits at all?
All the best,
I've had people quote "flattering rejection notes" in their queries to me. 99.9% of the time they are quoting form letters.
Don't mention rejections in your queries to agents and editors. Not even those with Killer Yapp's delicate pink snout prints on the signature line.