Originally Posted by babyd
I think you need to put 'Convert' in the subject line of the email if you wish it to be converted, then send to email@example.com
You only have to do that if you're sending a PDF and want it converted to .azw. Without specifying "Convert", Amazon just delivers PDFs. Any other supported file, even natively readable .mobi and .prc, Amazon converts to .azw before sending, whether you've put anything in the subject line or not.
Another tip: You can set your Personal Document Charge limit to $0.01 (on Manage Your Kindle). Then, if you send something to *@kindle.com, you'll get a message saying that the charge was over the limit, and they'll automatically forward the document to *@free.kindle.com. That way, you can still get files for free from sites that don't support the free address (like Instapaper). But, if you ever want to receive files over 3G, you'll have to change the limit first.