A legible font refers to a type of writing style that is easy to read and understand. It is clear and distinct, making it comfortable for the eyes to decipher the letters and words. Full definition
The information should be in legible font preferably the most standard font used for business communication. (topsampleresume.com)
Readability is the next important design tip: you want your emails to be as easy to read as possible by not being afraid of white space, dividing content into sections, choosing legible fonts within the 14 - 16px range, and adding a clear call to action. (creativeboom.com)