Is that really the best idea? Or would it be better to have a "upcoming service" form or report that shows when the application starts. Then everyone can see every day what is upcoming. Another alternative is to use the Reminder feature of Outlook
itself.
Assuming you really want to go the email route, the next thing you will need is working knowledge of queries and VBA. If you don't have that, you may have the hire the necessary talent.
This code would run at startup of your application and checks if any reminders need to be sent that have not yet been sent. It then sends the emails (maybe it's a simple report that can be sent using DoCmd.SendObject) and updates a table that they have been
sent. This flag also needs to be cleared again at some point (maybe after the maintenance is done, so it will be triggered again at the next interval.
-Tom. Microsoft Access MVP