I use Apple Mail to manage emails from multiple accounts because of it no-frills UI which follows the macOS design language to the letter. But then the app is so bare bones that it does not even have a simple reminder option for email to follow up—at least not in a very intuitive way.
To add a reminder on your email you need to use the Reminders app from Apple. See how Apple tries to hook you up in their ecosystem. Follow the below steps.
1. In your Apple Mail app select the subject of your email and right click. This is a key step so that the reminder opens up the email that you want to follow up on. Click on Share > Reminders. On iOS you follow the same steps—select the Subject, tap on Share and select the Reminders app.
2. You will get a dialog similar the one below where you can set the date and time for reminder. Note the Mail icon being shown in the dialog. Click on the Add button.
3. The reminder should be added in the Reminders app with the Mail icon. Tapping on it will redirect you to the email.
