Outlook 2016 used css2, which was about 20 years out of date in 2016, but at least it was a standard, with documentation, and decently reasonable for the year it was agreed upon by the WWC. For Office 2019 they went backwards and switched Outlook to use the Word renderer. Anyone who has ever had to make an advanced email template for Outlook 2019 and later has a deep, burning hatred for Microsoft that exceeds even their hatred of IE.
Outlook 2016 used css2, which was about 20 years out of date in 2016, but at least it was a standard, with documentation, and decently reasonable for the year it was agreed upon by the WWC. For Office 2019 they went backwards and switched Outlook to use the Word renderer. Anyone who has ever had to make an advanced email template for Outlook 2019 and later has a deep, burning hatred for Microsoft that exceeds even their hatred of IE.