Check if a customer has an existing Azure AD Tenant
I deal with onboarding a lot of customers into CSP, and many of those don't understand their current Azure Active Directory usage, or even if they currently have Azure AD.
If I want to check if a customer has an associated Azure AD tenant myself, there's no built in way in either the CSP or Azure AD portals to do this.
Luckily, the site Office 365 Rocks exists, which can check tenant availability.
Often just by sticking a company name in there I can find if a customer has created a tenant previously, whether they realise it or not.