What are customers of an IT service provider who purchase services in terms of a legally binding contract known as?

Strategic customers is not a standard ITIL classification for customers who purchase services via contract; it is not a defined customer type in ITIL terminology.

External customers are defined in ITIL as customers who are not part of the same organization as the IT service provider and who purchase services through a legally binding contract. This distinguishes them from internal customers, who are departments or business units within the same organization. The contractual relationship is the key characteristic that defines external customers.

Valued customers is not a recognized ITIL customer category; all customers may be considered valued, but this is not a formal technical classification.

Internal customers are employees, departments, or business units that are part of the same organization as the IT service provider, not external contract-based purchasers.