When I send .jpg attachments using Mail, for some users they arrive embedded in the email instead of as attachments. Is there a solution for this?
John Gage

There certainly is. Compose your mail as normal, then attach your image. In the Choose File dialog, make sure Windows-Friendly Attachments is checked. When you’ve chosen a file and it appears in the mail window, hold down Control and click on the image and choose View as Icon.

If you have more than one image to send, select them all in Finder, Control-click on a highlighted file and choose Compress x Items from the pop-up menu. You can then send the bundle of images as a PC-friendly ZIP file instead.