The risks posed by inactive (dormant) users present on an organisation's servers are a potential goldmine for malicious attackers but also serve to highlight poor user management processes. Indeed, both the ISO 27001 control framework and the PCI DSS information security standard require organisations to monitor, act, and also report on these inactive users.
The users on your MobileIron servers are no different, but are often overlooked.
Identifying users who are still present on your server, but do not have associated devices attached to them, is not trivial. However IronWorks can help in this regard as well: not only identifying them, but also allowing you to report on these over time.