Embed Videos in a Salesforce Classic Email Template

Perform the following steps:

1. Take a screenshot of your video and crop the image to the video content (remove any on-screen controls).
2. Find an image of a play button online (look for one with a transparent background).
3. In a photo editor, overlay the image of the play button on the image of the video (typically in the middle).
4. Save this edited image as a single image.
5. Upload the image under the Documents tab (you may visit this documentation for reference: Upload and Replace Items on the Documents Tab).
6. Once the image has been uploaded, get its Image address (right-click then copy the Image Address).
7. Edit the desired Classic Email Template and place the video at the desired location.  Here is a sample snippet below:

<a href="PASTE_VIDEO_URL_LINK_HERE"><img src="PASTE_IMAGE_ADDRESS_HERE"></a>