No one else I send files to report any problems. He also says he doesn't get problems with other sender's attachments. I'll investigate SGilberts idea that perhaps sometimes I am sending HEIC files.If your edited JPEG is still a JPEG (check this to make sure), you should not expect a problem viewing an attachment on a standard system.
Does your friend get any kind of similar attachments, with no problems, from other people?
If you send your jpeg to someone else, do THEY have any difficulty opening your attached file?