A lot of old 90's "hacks" are still commonplace in current email design. Thanks to Outlook's reliance on a brain dead MS Word-based rendering system rather than using actual modern HTML5.
And since Outlook is still the standard for email clients in the workplace, all other systems are impacted as well.
It's interesting to see modern day developers struggle with email design and turn to folks like us :D
Honestly, at this point we should classify "Email HTML" as a different subspecies than regular ol' Web HTML. They evolved from a common ancestor, sure, but Email HTML is like some sort of flightless bird on a remote Pacific island: it kinda just... stopped.
And since Outlook is still the standard for email clients in the workplace, all other systems are impacted as well.
It's interesting to see modern day developers struggle with email design and turn to folks like us :D