Spell check!
I think that spell check and grammar check would be CRUCIAL in emails to the customer. I type Fast, and sometimes I may miss a letter, or may not have the proper grammar for certain sentences and second guess myself if it sounds professional.
I would LOVE the opportunity to have those apart of my services so I don’t have to copy and paste my templates to my Microsoft word to get that benefit before I send out a professional email that reflects directly on my business.