The similarities to Gmail aren’t coincidental though. The Yahoo CEO Marissa Mayer helped design some of Gmail’s features while she was a top executive at Google. Since its debut nearly a decade ago, Gmail has steadily grown into the world’s most popular email service. Yahoo’s redesigned email unveiled includes a Gmail-like tool that will thread together emails related to specific topics so they appear as a succession of messages. Another new feature will enable Yahoo’s email users to decorate their inboxes with pictures plucked from the company’s photo-sharing service, Flickr. Gmail has been allowing its users to spruce up their inboxes with various themes for years.