I just logged into my Yahoo email and successfully sent an email with attached jpg to my ISP email address.
I opened new message; clicked on - 'attach files from computer'; when the window popped up with my computer files, I searched for and selected a jpg of a bull elephant in my Pictures Folder; then clicked OPEN, which is in lower right corner of file window.
The bull elephant jpg was visible on bottom of my Yahoo email. I typed in my ISP email and typed a subject, and hit SEND.
It took awhile but it finally showed up in my ISP inbox. I clicked on bull elephant jpg and jpg opened with the W10 basic PHOTO app . Worked great, although Yahoo does seem a little slow in sending my email with photo.
Maybe your jpg is too large? Yahoo may have 25MB attachment size limit?
I watch safari LIVE and do some screenshots (bull elle), like they tell you to. This week there is big migration at Maasai Mara in Kenya, LIVE on YouTube twice each day, 7 days per week, FREE, Friday night also on Nat Geo Wild channel (or YouTube).