Nokia recently announced the start of the Windows Phone 7.8 update rollout for its Windows Phone 7.5-powered Lumia handsets, but it looks like there's one U.S. carrier-branded handset that won't be receiving the new software. T-Mobile has confirmed both in a statement to TmoNews and in a post on its official support forums that the the Lumia 710 will not be getting a bump up to Windows Phone 7.8. The Magenta operator doesn't explain exactly why the Lumia 710 isn't receiving a 7.8 update, saying only that it "aims to deliver software upgrades when it will provide a better experience for our customers." Here's the full statement on the matter that was given to TmoNews:

"At this time, the Nokia Lumia 710 will not receive the software update. T-Mobile is committed to enhancing customers’ experience with our devices, including providing upgrades to the latest operating systems, and T-Mobile aims to deliver software upgrades when it will provide a better experience for our customers. We’ll share additional information on upgrades for the Nokia Lumia 710 when they are available."

The Windows Phone 7.8 update brings some Windows Phone 8 features down to Windows Phone 7.5 devices, including a new Start screen, resizable live tiles, new accent colors and the Bing wallpaper of the day. That may not sound like much, but the update can help to breathe a bit of new life into an older handset. Now it looks like Lumia 710 owners on T-Mobile will have to upgrade to a new Windows Phone 8 handset like the Lumia 810 if they want those new features, though I'm sure there are some 710 folk that'll be hesitant to go that route after today's news. If T-Mobile issues any other comments on this situation, we'll be sure to update you. Do any of you out there own a Lumia 710 on T-Mobile?

Via TmoNews, T-Mobile Support