Near the bottom of the e-mail is this paragraph
the Auto-Renewal Plan to Avast Software a.s. (“Avast”), in which case Digital River will transfer your billing information to Avast or their payment processor, and Avast’s terms of sale and privacy policy provided to you in Avast’s reminder email will apply to each renewal transaction.
You may cancel your auto-renewal plan at any time by logging into the My Subscriptions portal (access information are included in this email or on the Customer Service Help page), selecting your product, and selecting the option to disable automatic renewal.
Click the link for “My Subscriptions Portal” on that page will be the option to disable auto renewal