Certificate not trusted

I got a notification saying certificate not trusted for an email that is not mine. My iphone is new and there‘s no such email anywhere. I checked the certificate trust settings on my phone and i couldn’t find anything that needs to be verified. This is the first time this shows. Is my iphone hacked? Where did this email and notification pop from? When i check the details of the notification i did not verify it, i just pressed cancel but the details looked susipicious. However, when i turned my hotspot off and disconnected from a public wifi the notification stopped showing.