There is a huge amount of nuance to what will work in emails. I built the lion's share of the WYSIWYG email editor for ActiveCampaign a few years back, and got

There is a huge amount of nuance to what will work in emails. I built the lion's share of the WYSIWYG email editor for ActiveCampaign a few years back, and got quite a few horror stories out of it. There are a lot of tricks that have to be learned, and a lot of trial and error, but responsive emails, that look the same(ish) across most browsers and email clients are possible. I wouldn't want to generate the HTML myself though, as email is stuck ~10 years in the past compared to the web.