Change line height in emails

Hello there ! 

I would like to change the line height of the paragraphs of my newsletter but there no any "official" way to do so. I'd like to know id I can do it by adding custom code inside my site ? 

Thanks to anyone who can help me ! 

Me too! It's been a super frustrating experience with the line height all over the place. Looks bad and that I can't design! Any help is appreciated. Maybe @sgreisdorf can point us in the right direction?