Why is it not recommended to use a corporate domain as the CRM Approved Email Sending Domain?
The corporate domain is usually the main domain name that is chosen to represent the website address. The main controls for the server is shown under this domain.
The reason why it is not recommended to use a corporate domain as the Approved Email Sending Domain is that the corporate domain might be used by other services which can impact the delivery of emails. Since SPF records are created against the corporate domain, they likely break any existing integrations.
We recommend to use a subdomain instead, such as 'm.company.com' or 'ae.company.com' and create DNS records against the subdomain. This way, the corporate domain is not affected.
A subdomain is an additional part of the corporate domain name. Subdomains are created to organize and navigate to different sections of the website.
CRM Help Documentation: Creating a Sending Domain