My approach would be to have subject "Check and revise the priority of Redmine issue (#455)". I'd then put an explanation in the body of the email. That puts th

My approach would be to have subject "Check and revise the priority of Redmine issue (#455)". I'd then put an explanation in the body of the email. That puts the task in the inbox, and they can open it if they want to see the details again later. This has helped me when there are multiple things that have to be done. I now usually send several messages rather than one, with one task per email. In the cases that is not practical, I make it clear in the subject that there are several things to be done, and the body starts with a list of all the tasks.