I use an email add-on called YesWare.
If it becomes irrelevant before it’s sent, just cancel it. I see my prescheduled emails in my drafts folder. This picture shows an image of an email going out tomorrow. This tool has other key features, too, but since we’re on the subject of follow-up, I thought I’d highlight it. Let them know The Growth Coach sent you.
If you don’t want to use a tool like this, then simply add a task with a deadline to follow-up with people so you don’t forget.