I had a go at trying to beautify emails sent out from my app and I discovered that most of the formatting I had put in the template was missing when I got the email in gmail.
So I created a test document in Google docs and used that as a template. The test document looked like this:
When I received the mail in gmail, it looked like this:
So not exactly WYSIWIG.
I then discovered that the problem only occurred using the gmail client in a browser or on android. Yahoo emails were fine as was viewing the email sent to a gmail account in another email client (Thunderbird). Conversely, the email sent to a yahoo email address lost its formatting when viewed in the gmail client. I haven’t tried outlook. I am not a heavy Microsoft user.
How different email clients render HTML is really not something I know a lot about so I may be barking up the wrong tree here but it seems that the gmail clients are struggling when the formatting is in classes rather than inline. Or it could depend on where/when the classes are defined.
Btw, downloading the HTML code from Google docs and pasting that into an email also results in the formatting being lost so I guess there is an argument that this is not an appsheet problem.
A workaround that works is to use a word document. I think this is because Word uses inline formatting when rendering HTML. It also works to upload a word document to Google drive, edit in it docx format on google drive and using it as a template for appsheet. So If I copy the content of my test template to and empty word document on drive that will then be pretty much identical to the Google document I had, the HMTL rendered for the email works also in a gmail client.