Why do I see an "external recipients" alert when sending an email to someone in the Outlook mobile app?
Explains why a banner appears in Outlook mobile app when sending email to non-UIC recipients.
On March 4, 2019, Microsoft released a security enhancement to Outlook for iOS and Android. This update helps to protect sensitive information from being sent outside the organization. The update causes the Outlook mobile app to display an alert that you are sending a message or reply to recipients outside of UIC.
You do not need to do anything differently before sending your email - the purpose of the alert is to raise your awareness that the email you are sending is going outside of UIC.
NOTE: The "Replying to external recipients" message will also appear for email addresses ending in @uillinois.edu, @uis.edu, and @illinois.edu, as the other entities of the University of Illinois System are not on the same email infrastructure as UIC.