When a word is underlined in your email, it means there’s a Yahoo! Shortcut waiting to save you time. By hovering over the underlined word or phrase with your mouse, you’ll see a little menu of things to do—like adding someone’s info to your address book, getting a map of an address, or searching for more info on a topic.
Yahoo! Mail underlines email addresses, phone numbers, and physical addresses and locations. We're also working on other terms to turn into Yahoo! Shortcuts. They’re coming soon, so be on the lookout.