When I receive an email from anyone, whether they represent a company or not, it's private, otherwise they might as well put it up on my FB. It works in reverse for anyone sending me an email and thusly I never post emails publicly without specific permission and removing names etc...
If you think otherwise feel free to give me the password to your email account.
So if you got an email from, say, Bed Bath and Beyond advertising 50% off Widgets this Sunday and you participated in a Widget fan forum, you would try to contact Bed Bath and Beyond to get permission to share the e-mail first?