Thanks for reaching out. We're here to help. Are you using Lightroom Classic or Lightroom Cloud-based? Which version of Lightroom are you using? Can you try out the steps mentioned below and let us know if it helps.
STEP ONE: Click on the photo(s) you want to email, then go to the File Menu and choose Email Photo (as shown here).
STEP TWO: This brings up this intermediary window where you enter the email address of the person you want to send the image to, along with your subject. It will choose your computer's default Email application, but if you use a different one, you can select it from the 'From' menu. At the bottom, you can choose your desired size and quality. When you hit the Send button, it doesn't send — instead, it opens your email client with your image attached and all the fields completed. You can enter any additional text or just hit the Send button in your email client, and away it goes.
Try out these steps and let us know how it goes.