That "mess" happened in one Maryland office when a co-worker hit reply all and made a racial slur and sexual comments. She was moved to another position.
For Post, and many others, one e-mail faux pas trumps them all: writing missives in ALL CAPS.
"All caps is the No. 1 worst offense. It's the e-mail equivalent of shouting," Post says. "It's makes me cringe when I get an e-mail in all caps, no matter how nicely it's written."
For Pamela Eyring, the owner and director of the Protocol School of Washington, correct grammar and punctuation — whether it's avoiding the all caps curse or using spell check — is essential.
"When you're doing e-mails, the first thing you have to remember is that your e-mails reflect you," Eyring says. "So that e-mail courtesy is just like writing someone a letter: [You need] correct grammar, spelling and punctuation.
Eyring says that's all part of knowing the audience. For some younger students that she teaches, that means stressing avoidance of shorthand like OMG or btw.
"Not everyone gets it unless you're in that same culture," she says.
All of these things contribute to one major pitfall of e-mail, according to Schwalbe: It is unable to communicate tone.
"Balance is something that people forget in e-mail: Close as they close. Address people as they address you," he says. "If you signed something 'love' and they wrote back and closed with 'sincerely' clearly you have different ideas about your relationship."
But for all the talk of rules and etiquette, accidents happen.
When I started working on this story, I even broke one of my own personal e-mail rules: Honor thy friends' privacy. As I blasted out a message to my acquaintances wanting to hear their e-mail horror stories, I accidentally placed addresses in the CC box, instead of the BCC box. As soon as I sent the e-mail, I recoiled.
"For mass mailings always use the BCC line if it's something really large in your social life in terms of privacy," Post says. "No one wants the reply all button on that one."
Indeed. I feared receiving a response that said, "My e-mail pet peeve is you!"