working in MOE HQ for 12 years. 2 pcs of advice to give. don't beat yourself too much over email etiqutte. everyone has different tolerance level. generally we are quite chill over the choice of words as long as the tone is OK. over time, you get a feel of the right tone.

2nd pt is that there is surely some senior or mentor figure (not necessarily your RO) in your section, that can help you vet submissions and double check. pointing out mistake AFTER you send email is counterproductive. better to send it to one person, WA him/her to ask gor help to review and learn from the edits made.

we want to set up our fellow colleagues for success and not doomed for failure.