Imagine my surprise to find out an email I sent in response to a query letter had been sucked up in the spam filter. Fortunately the querier saw it and did respond in a timely enough fashion that she didn't get a nice rejection letter for Thanksgiving.
A word to the wise, Snarklings: when you query, even by snail mail, you may hear from us electronically. Don't send us to SpamLand. You won't have our email addresses on your approved list, you'll have to either watch carefully, or use a fresh email address without the spam blockers. The email address I use to write to people is NOT the same one that is on my website, so you can't just add me in to your approved list before hand.
If I email someone with a question I usually only wait about a day or two to hear back, then I send a rejection. I can't let queries sit here for days on end or I'd be buried.