Hi turtlejane,
Thanks for using the Apple Support Communities.
Rest assured that you didn't do anything to enable this feature. Follow up suggestions are a Mail feature with macOS Ventura, and we can help you get this working to your preference.
Take a look at the information below:
Get reminded to follow up on emails with no response
If you send a message and don’t receive a response in 3 days, the sent email automatically resurfaces to the top of your inbox to help you remember to follow up.
- To ignore a follow-up suggestion, swipe right on the message in the message list.
- To turn this feature on or off, choose Mail > Settings, click General, then select or deselect the checkbox next to “Enable message follow up suggestions.”
Reply to, forward, or follow up on emails in Mail on Mac
That last option should have this disabled if that's your preference.
Best of luck!
Thanks for using the Apple Support Communities.