Can a user Opt-Out of all Email Addresses on an Account at the same time from CRM?
It is not possible to Opt-Out of all Email Addresses on an account at the same time. The opt out record is associated with the email Address and not just the Account.
Switching the Approved Email Consent Type to Explicit Opt In is one option that prevents this. Another option is to create a trigger and create MC consent records for all email Addresses on the Account and Address object.
If the accounts have more than one email Address, then switching the consent to explicit is the best solution.
CRM Help Documentation: Capturing Consent for Approved Email