How to change standard font type in mail for plain text

asked 2015-02-04 20:40:35 +0300

elastic
1395 ●23 ●33 ●38

updated 2015-02-04 20:43:22 +0300

As I really don't like serif fonts on smaller displays, I wonder how I could change the standard font in the mail app for plain text messages ... thx