Besides obvious spelling and grammatical errors, here are 6 ways to accidentally look unprofessional to customers via email (in other words, don't make these mistakes):
Some of the most popular abbreviations that have essentially become slang in the email world include "thx" and "lol." Hopefully, seeing some of these abbreviations actually makes you cringe a little. We live in a world where we have become so accustomed to texting, and abbreviations make it considerably easier for our fingers to manipulate the small keyboards on our smartphones. While you may be able to pull abbreviations off in a personal setting, don't ever give them a go when attempting to send a professional email.
2. Too much punctuation
Yes, you want to incorporate some personality into your content, but overusing punctuation (i.e.: !!!!!!!!!!!!) is not the way to do it. Doing this is almost as bad as writing a work email using all caps. While there are certainly times that call for an exclamation point to be used, carefully consider the context of your email and how you want your content to be received by your audience.
3. Emoticons ;)
So many of us send emails from our smartphones, and at times, it can be incredibly tempting to throw in a "cute" emoticon or two to get the message across. Avoid this temptation. Emoticons have a tendency to bring a "teeny bopper" element to your emails, which is likely not the vibe that you want to give off to your customers and other professional relationships. If you feel that the content in your email requires a smiley face, consider rewriting it.
4. Sending a one word response
Yes, you're an unbelievably busy and important business professional; however, when you send the dreaded one word reply to an email, you are basically telling that person that you don't have time for him or her. There is certainly no need to write a book with your response, but at least take a minute to write a clear one sentence response.
5. Replying to all
There are definitely times when it's appropriate to hit the "reply all" button in an email. However, consider the number of recipients on your email and the people that really do need to know your response before hitting this button. The last thing you want to do is share confidential information with your client's office staff.
6. Using special email signatures for mobile devices
We've all seen the "sent from my iPhone, please excuse any typos" email signature. To me, this seems to take away from the importance of the way that you handle emails, especially in a business setting. Simply take an extra minute to proofread your email before hitting send, just as you would if sending an email from your desktop computer. A simple "Sent from my iPhone" is acceptable, but don't apologize for a mistake you're perfectly capable of not making. It translates to "I didn't care enough about this email to reread my response".
It's easy to get caught up in a busy day, making it even easier to skip over the rules for proper email etiquette. When communicating with clients, prospects, and vendors, be sure to take a few extra seconds and make sure the content in your email is best representative of your business, brand, and professionalism.