Hi,
I believe the company is using the Active Directory for storing username and password for it's employees; meaning the employees have their accounts in the Active Directory of the company against which the username and password are validated. If that
is the case, and the Dynamics CRM 2013 is an On-Premise one, the same username and password can be used to validate the login. Dynamics CRM On premise, by default, authenticates users against the active directory, meaning the users in Dynamics CRM are
that of AD.
Admin QuikView Solution for CRM 2013