I'm using a template and when I click on the image and add text to the Alt Text field, then send a test email to myself in Outlook, the alt text does not show up even though I'm not downloading images. If I create an HTML email using my own HTML, it works. Can you check on this?
My folks here took a look and think the problem is likely due to the quotes in the alt text. Please give this a try and let me know if you see the results we saw. If not...let me know as well and we can see if there isn't something else going on.