Post by Email (JetPack 2.2.5) intermittently returns an email saying:
Some attachments were rejected from the following WordPress.com Post by Email: - Long Term Whiplash.jpg - Invalid response from the Jetpack site. When this happens, the featured image sets, but the email is not inserted into the post. I do have an A record set up for this domain.
See the physical therapy blog here: http://stsmpt.nwsltr.info/