SAN FRANCISCO -- Yahoo is trying to phase out passwords with an update to its mobile application for its e-mail service.

The renovated app released Thursday for iPhones and Android devices will include an option called "Account Key" that allows people to sign into their e-mail accounts by pressing on a notification sent to their smartphones instead of typing in a password.

Yahoo believes the new feature will be more secure because most people rely on passwords that are easy for hackers to guess. Yahoo's email users can still continue to type in a password if they prefer.

Although Yahoo e-mail remains among the world's most popular, it has been eclipsed in recent years by Google's Gmail. Yahoo's e-mail had 190 million user in August, a 16% decline from the same time last year, according to the research firm comScore. Gmail boasted 411 million, a 5% increase.

The updated app also will make it possible to connect Yahoo email with competing services from Outlook.com, Hotmail and AOL. The Sunnyvale, Calif., company hopes to make the app work with Gmail eventually, though it isn't giving a timetable for making it happen.

An update to the Gmail app earlier this year allowed its users to connect with Yahoo e-mail and Microsoft's Outlook.com.

The app update is important to Yahoo because more than half of its e-mail users primarily check their messages on mobile devices. E-mail users also are an important source of traffic at Yahoo's other major services, including sports, entertainment and finance that help sell the advertising that generates most of the company's revenue.

Yahoo's revenue has been declining or barely growing for years as advertisers pour more of their money into Google and Facebook.