This guide is intended to give you some ideas about how to generate an eduPersonPrincipalName (ePPN) for users.
You can find a video introduction to ePPN on Skolfederation's YouTube channel here (in Swedish).
eduPersonPrincipalName is defined in eduPerson 1.0, OID:126.96.36.199.4.1.59188.8.131.52.6
A scoped identifier for a person. It should be represented in the form "user@scope" where 'user' is a name-based identifier for the person and where the "scope" portion MUST be the administrative domain of the identity system where the identifier was created and assigned. Each value of 'scope' defines a namespace within which the assigned identifiers MUST be unique. Given this rule, if two eduPersonPrincipalName (ePPN) values are the same at a given point in time, they refer to the same person. There must be one and only one "@" sign in valid values of eduPersonPrincipalName.