If an account is signed into using a device not recognized by the account, a notification
e-mail is sent to the account’s e-mail address “to make sure it’s you.” But if someone
else has signed into the account, they can delete (and then permanently delete) that
e-mail, so what’s the point?
If you have multiple devices that email will be visible on those devices as well. Deleting it from device a won’t necessarily remove notifications device b.