ugh, know that feeling. I pride myself in correct spelling and grammar in my professional communications too, I have to as it is part of my job to ensure that it is correct on all documents that go out to clients. I spend so much time arguing with people about the fact that I have corrected it because it was wrong originally. We also have brand guidelines we have to stick to, like we can't put st, th, rd or nd after numbers in dates, we are required to use just the number. We are also not allowed to use any capital letters at the start of bullet points, unless it is a proper noun of some kind, or have any punctuation at the end of each bullet point. This is the biggest bone on contention as everyone wants capitals at the start and commas, full stops or semi colons at the end and keep putting them back in or telling me off for removing them. What they don't seem to be able to get into their heads is it's not just my preference, it's a rule dictated by our ultimate parent company, it's not optional or changeable!!
I wouldn't worry too much about your email, if you had sent it out to most people in the correct form then that's good and, to be perfectly honest, most people don't tend to notice bad grammar as much as those of us who have to pay attention to it do!
xxx