Microsoft revealed on Thursday that it is now delivering the Windows Phone 7.5 update to HTC HD7S devices on the AT&T network.

AT&T users in the U.S. will start to see the Windows Phone 7.5 “Mango” update show up on their devices from Thursday. Microsoft is still delivering the Windows Phone 7.5 update to 50% of Windows Phone users. Microsoft’s Eric Hautala, in charge of Windows Phone update deliveries, had no further information to share on additional devices for Mango. “We’ve just started delivering Windows Phone 7.5 updates to the the HTC HD7S on AT&T. If you have any questions about how to install or manually check for an update, please visit Update Central.”

Spanish operator Telefonica is still testing its Mango update for devices. “I’ve seen some questions here and on Facebook about phones still listed as testing on Where’s My Phone Update?” said Hautala on Wednesday. “ If you own one, I want to reassure you that we’re working closely with carriers to complete testing and are making good progress.” Microsoft will add more phones to the Windows Phone 7.5 update pool in the coming weeks. AT&T customers with the Samsung Focus v. 1.4 and Dell Venue Pro are still waiting for the carrier to complete testing.