I made what they wanted with MJML. Looked good in a browser, gmail and phone.
Outlook had a few issues, can't remember which right now.
But replying from Outlook simply broke the styling completely. Gaps between each section, complete mess. Not the impression you want to give the customers when their order goes wrong. B2B means Outlook is what out customers use.
I've found that replying via Outlook is the ultimate integrity test of an eamil.
Now I'm making them by hand and it is a madening cargo cult bonanza. Takes a lot of time.
I guess MJML is fine for marketing.