Does read my emails? scans your email headers to better understand who you speak with to make better decisions when you ask it to complete a task. None of your email headers is stored nor is any email content read.
If you're an enterprise user, your admin can restrict Email permission access. If your admin has not restricted email permission, then you're given the choice to allow at the user level.

You also have the option to not allow this email permission when you authorize access during registration. You can still later update this from "Settings > Account" by checking 'Email on the applicable provider'.