As part of its continuing effort to modernize its suite of products, Yahoo announced a significant redesign of Yahoo Mail, including a new compose screen, collapsible toolbar and improved threaded conversations. The updates are currently rolling out across the Web, Android, iOS and Windows 8 devices, the company said.

Many of Yahoo Mail's updates play catch up to Google's Gmail offering, which now has more than 425 million monthly users. Yahoo's "conversations" introduce emails grouped in threads, adding more context to conversations. Common actions, such as searching for, starring and deleting emails, are introduced as one-click actions that appear when you hover over an email. You can also now collapse the left-side toolbar.

Jeffrey Bonforte, Yahoo's senior VP of communication products, said that the company is launching these updates to celebrate Yahoo's 16th birthday. "Since it's not a birthday without party favors, we're making many features previously reserved for premium Mail Plus customers free."

Mail Plus was Yahoo's ad-free email service, which users could purchase for $20 per year. Mail Plus features that all users can now access include disposable email addresses, in which you can create an email address when you don't want to give out your primary one; up to 200 enhanced filters to help sort incoming messages; automatic message forwarding and offline access. All Yahoo Mail users are also receiving increased storage, now capped at 1 TB.

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If you are a current Mail Plus user, you will be ported over to Yahoo's new ad-free email service, called "Ad Free Mail." This type of email account is free of text or graphic ads and won't go inactive if it's not used, the company said. New Ad Free Yahoo Mail accounts don't come cheap, though; they cost $50 per year. Mail Plus users will continue to pay the $20 per year price.

Last, Yahoo is introducing new inbox themes for your browser, smartphone and tablet that include curated Flickr photos. This lets you choose a new photo theme in one place and it will apply to all devices.

Yahoo has placed a significant emphasis on email this year, most recently coming under fire for privacy and security concerns surrounding its recycled email initiative. Users were allowed to sign up for previously owned, dormant email addresses, but quickly reported receiving personal emails intended for the former account owner.

Yahoo responded to concerns with a "Not My Email" button, which it said will help train inboxes to recognize which mail belongs to them. Security experts immediately admonished the company's response, saying it didn't address the initiative's core security and privacy problems.

Yahoo's redesigned mail interface is now live for desktop users in the United States, Canada, United Kingdom, Philippines, Malaysia, India, Ireland, New Zealand and South Africa, the company said. Yahoo Mail's mobile apps are available for download at the Apple App Store, Google Play and the Windows Store.