The "Notification Email" functionality in Box is very helpful for @mentions, file sharing invites and other user notificaitons that need to go to an email address other than the email address used to sign into Box. This can be the necessary when a company has subsidiaries on a common directory infrastructure, but one or more subsidiaries is still maintain the old email identities for day to day work. There are likely other reasons to use this field.

Email: john.doe@mothership.com (Used to sign in.)
Notification email: jdoe@subsidary.com (The correct email address for user notifications.)

Box's SAML integration allows an Identify Provider, Okta for instance, to provision a new user which is great. However, it's not presently possible to populate the data element for "Notification Email" via SAML. This requires a time consuming manual update in Box when setting up a new user.