I run Windows 10 and use a gmail account which receives all messages just fine. I use Outlook 2007 to read the emails and separate into several folders. By this means I can delete emails I do not want to keep as gmail saves everything. The only time I have a Outlook problem is this list. Some get converted to attachments .txt and .htm, and some come through just fine.
I googled "why does outlook change incoming email to attachments". It is most apparent this has been an ongoing problem for Outlook for many years. Several threads with Microsoft Tech Help are listed. I am no computer genius so have no idea what they are talking about but one thing did stand out for me. Having URL or attachments in the body or at the end of the sender's email is a probable cause for the issue for the recipient if using Outlook. There are fixes per Microsoft which could explain why some senders work fine and others do not depending on how their particular computers are set up and how up to date they are. My thought would be to try removing the cutting board notice for a while and see what happens? Also is there a computer genius who could coordinate with Stu, review the various threads and perhaps contact Microsoft? My 2 cents American John Read Legacy III 1982 C&C 34 Noank, CT Customized C&C Cutting Boards available at: http://www.cncphotoalbum.com/cutting_boards