Absolutely. Just add your files to your emails, and Sifter will take care of the rest. This works really well with images, and Sifter even takes steps to ensure that your comment threads aren't flooded with corporate logos from email signatures.
There are a couple of caveats, though. Due to the way that the variety of available email clients handle HTML, you'll need to zip up any HTML files you want to upload via email. Similarly, some documents like Pages, Keynote, or Numbers, are actually directories rather than files, and you'll need to zip those up as well for us to handle them correctly. If in doubt, try zipping up your files before sending them.
If you notice any unusual behavioral at all, please let us know. There's an incredible amount of edge cases, and we can usually update the code to handle them if we have a sample problem file to test against.