When UiPath robot is trying to read emails from Outlook, a dialog box pops up

When the robot is trying to access Outlook for sending or reading emails, a security warning pop-up appears : "A program is trying to access email address information stored in outlook"

These security warnings appear when a program attempts to access your contact information in the Outlook Address Book, or attempts to send email on your behalf.

By default, only COM add-ins are trusted programs. Your email administrator may have allowed specific add-ins by adding them to a "Trusted add-ins" list. Any other program isn’t trusted, and a security warning appears because of the potential risk that the program is malicious and designed to use Outlook to spread viruses.

From Trust Center -> Programmatic Access settings set the programmatic access to Never warn me about suspicious activity (not recommended). 

For more details check here .