Mac email attachments aren't encoded properly?

While interoperability between Mac and Windows systems has come a long way in the last decade, and it's rare to have Mac users wishing they were using a Windows system so things wouldn't be messed up on transfer, there are occasional hiccups and glitches that can prove frustrating problems, particularly with email applications. A reader wrote in asking about a strange incompatibility with his attachments when sent from his Mac to other Mac users and Windows users, and it turns out that the most probable answer is pretty easy:

    Mac email attachments are broken

Windows zealots will particularly appreciate my answer. :-)