Yes, you can turn off any emails that you do not want to utilize, although this is not recommended.
By providing automated emails to your channel subscribers you significantly improve attendance at live webinars and viewing of recorded content. Turning off these emails reduces your touch points with your registrants.
To disable an email, go to the channel management area for your channel. Then, select the Promotion tab. On the left, you'll see a link "BrightTALK email service". If you go there, you'll see a list of all the emails that you channel sends. Look for the email you want to disable and choose Edit. On that page, there will be a button to "Switch off" the email.