Question:

Can CRM Approved Email be set up with Opt-In disabled? 

Answer:

Approved Email in Veeva CRM setup can be configured to require or not require Opt-In.

Classic Consent has the options Opt-in Required and Opt-in Not Required. 
In Consent Capture, Consent Types can be set to Implicit or Explicit on the Default Consent Type, determining the default consent for that channel as opted in or opted out to the channel by default.
But there is not a Disabled option for Opt-In.

The standard configuration of Approved Email requires users to have Create, Read, and Edit access to the Multichannel_Consent_vod object. There is no Custom Setting that disables this functionality.

However, CRM supports the option to remove users' Create and Edit Object Level Security to the Multichannel_Consent_vod object.  This is the only way to disable the Email Opt-in option all together for Approved Email. The Approved Email Opt-In Setting should not be set as Required if using this configuration.

Related Documentation:

CRM Help Documentation: 

• Capturing Approved Email Opt-In Consent (Classic Consent)
• Capturing Consent for Approved Email (Consent Capture)