We've all said things we wish we could take back. But it is one thing to say something you regret and another entirely to write something that will now be immortalized on paper and can be shared and transferred forever. Monster tells you to avoid this by avoiding saying certain things in a professional email.
Leave these things out of all professional emails:
1. Informal language that makes you sound uneducated or immature
Work emails need to be kept free of all-lowercase letters, texting language (gr8, lol, thx) or informal greetings such as "Howdy." Same goes for emoticons. Remember that there is no reason why you should need emoticons when being professional.
2. Ramblings of any kind
This includes overly-long requests and unnecessary explanations. Have some consideration for other peoples' time and stay brief. No one needs to know too many details about things, just stick to the important information.
Take your disagreements offline - and have it out in a place where you do not leave a record of it. The last thing you need is for an email detailing a heated disagreement between you and a colleague to surface years later and make you look petty.
Arguments also tend to look a lot worse on text, especially because people say a lot of things on text that they wouldn't normally dare to face to face.
4. Don't resign via email
While it is completely acceptable to accept a job over email correspondence these days, resigning might not be.
It may be tempting to do it over email - it is a lot easier, after all. But be professional. Call up your boss, set up a meet and then do it face to face. As awkward as it might be, you will be happy you did it.
It will save your reputation for any future business dealings you might have with the company. Don't burn your bridges.