In her first major move since taking the helm at Yahoo in July, CEO Marissa Mayer on Tuesday unveiled an upgrade to Yahoo Mail, the once-ubiquitous email service that has since been eclipsed in popularity by Google's Gmail. In a post on Yahoo's blog, Mayer said the faster and cleaner interface would be available on all platforms, including the iPhone and Android:

You've told us loud and clear that you want fewer distractions when it comes to email. You want to quickly login, communicate, and get on with your day. And we've listened. Starting today, the new Yahoo! Mail is fast, easy and available anywhere you go.

Keeping users on Yahoo Mail is critical for the struggling company, which has been losing the battle for advertising dollars as its popularity dwindles. Email services are a perfect vehicle for advertisers, since they're "as close to personal delivery as you can get," says Larry Dignan at ZDNet. Furthermore, Yahoo Mail offers users "links to Yahoo content pages with expensive brand advertising on them," says Nicholas Carlson at Business Insider.

But it will be an uphill climb. While Yahoo Mail is the most popular webmail service, according to ComScore, the only major email service that has gained users (and a lot of them) in the past year has been Gmail. In addition, while Mayer has prioritized creating a "coherent mobile strategy," Yahoo in the past has "failed to keep up with rivals when it comes to integrating innovative mobile and social media features," says Reuters. Analysts say making Yahoo Mail consistent across all platforms is an important and necessary step in that direction. But the true test for Yahoo is if users will continue to use its products as they increasingly turn to smartphones as their principal method of accessing the internet.