Ask an employee to define the customer, and he or she will probably say, "Someone who buys from us." But what about internal customers? Colleagues, other departments, branches, suppliers? They are equally as important and deserve to have their problems and complaints taken seriously.
Low morale and a critical and suspicious environment will prompt employees to see customers as a nuisance and not the lifeblood of the business. Every employee needs to appreciate that they contribute to customer satisfaction even if they are working behind the scenes. Unhappy internal customers lead to unhappy external customers.
Source: CRM Daily, http://www.crm-daily.com