How To (Easily) Email Mac Photos Images That Are Compatible With Android (.jpg)?

Mac with 10.15.7.
When trying to send photos via the yahoo.com web interface via the ‘attach’ commend, the pix is sent as an.heic. Unfortunately some recipients use other operating systems that can not view.heic images.
When trying to send the same file using Mac Mail (the application), IF the image is sent in “original size” it DOES automatically convert it to.jpg. However, if I set the image size to a more reasonable size in the pulldown menu (say, large), it does NOT convert to.jpg but again sends the.heic file.
I do know ways to convert manually, but my partner isn’t into the bits and bytes and just wants emailed images to be viewable by her android and other friends.
What am I missing here, to return her to the golden days of yesteryear when everyone could view emailed photos?
—–
Jeff