Similarly, as federations proliferate, it becomes increasingly difficult to discover which IdP(s) a user is associated with. This is true for both the web and non-web case but is particularly acute for the latter, as many non-web authentication systems are not semantically rich enough on their own to allow for such ambiguities. For instance, in the case of an email provider, SMTP and IMAP do not have the ability for the server to request information from the client, beyond the client NAI, that the server would then use to decide between the multiple federations it is associated with. However, the building blocks do exist to add this functionality.