Outbound smtp email can be set at the farm level (Central Admin –> System Settings –> Configure outgoing e-mail settings) OR at the Web Application Level (Central Admin –> Application Management –> Manage Web Applications –> [select your web app] –> click the General Settings dropdown and select “Outgoing E-mail”

Handy to know when you glance at the farm-level settings, and notice you don’t have an outgoing server setup, yet emails are still being sent!