Good article by Grace Bonney at Design*Sponge:

Modern Etiquette: Email Correspondence

“I was so excited to tackle today’s etiquette post because, if you’re a blogger or someone who works online, you understand just how big a portion of our jobs email has become. From researching and interviewing to submissions and content management, email is the home base around which most of my business operates and returns to over and over again. Whether you’re a blogger, a business owner or someone who spends a lot of time on email, I can’t think of another area (aside from social media) that is so fraught with chances for huge snafus..”