Users - Considerations for data migration

When importing patrons from other systems, you should consider populating the emails for those patrons with a static email address that is associated with your migration so that you don't accidentally email people from your testing system.
When importing patrons from other systems, pay attention to the "preferred contact" field. As of Iris, FOLIO only supports email as a contact method with patrons, and if the preferred contact method for the patron record is email, it will attempt to email patrons even if they don't have an email address or if they have an email address that is invalid. In those cases, the circulation log will think the email was sent when it actually wasn't delivered all the way to the patron because the email was not valid.
As of Juniper, externalId must be unique (mod-user-import already enforced this, but it wasn't enforced in Users directly until Juniper.)