I noticed that none of my return emails to people who answered my craigslist ads were ever getting received. The problem appears to be with a new (to me?) craigslist feature that anonymizes the buyers' emails (well I should say the ad-answerers' emails) in addition to the seller's email like it has always done. This is going to get confusing so I'm going to use characters, Alice and Bob (but both are played by me in this re-enactment, both using my computer and my Apple Mail 3.6 with OS X 10.5, and I re-confirmed the problem using my iPod Touch's mail program, in iOS 6).
Alice posts an ad to CL, and CL anons Alice's email to "A". Bob answers the ad by clicking on the mailto link, opening a new email in Apple Mail, addressed to "A". Bob's email doesn't say anything about hiding Bob's address, and the reply-to field is empty. Bob sends the message, and Alice receives it. But when Alice receives it, Bob's real email address is not shown, and the "from" field shows an anonymized CL address "B". Alice then replies to this message in Apple Mail, addressed to "B", but Bob never receives the reply. Alice never receives an error message either.
So in summary, for some reason I can send emails to the ad poster's anonymized CL email address, but I can't send emails to the ad-answerer's anonymized CL email address, even though I'm using the same email app for both. Any guesses as to why, or what I can tell CL to get support? This happens in Mac Mail and iOS Mail, but not in gmail's website. Gmail is able to respond to these emails.
PS. If any of you answered a CL ad and got no response, sorry I tried