On April 23, Microsoft quietly made available for download a preview of its Remote Desktop app for Windows Phone 8.1.

Many Windows Phone users were none too happy that Microsoft delivered Remote Desktop apps for Android phones and iPhones last fall with no word on when it planned to introduce a Windows Phone version. In March, Microsoft updated the Remote Desktop apps for Android, iOS and Mac OS X , still with no word as to when or how it would provide remoting for Windows Phone.

Remote Desktop allows users to connect to remote Windows PCs and access resources from those machines. Remote Desktop has been one of the most popular Windows Store apps among Windows 8 and Windows RT users. The licensing requirements for these apps are complex . Client-access licenses and supporting back-end infrastructure are required to make Remote Desktop work on Windows and non-Windows devices.

Like the other existing Remote Desktop apps, the Windows Phone 8.1 preview version is free. It is 1 MB in size. It's available in the Windows Phone Store.

Windows Phone 8.1 is available in developer preview form only at this time. It is expected to come to new and existing Windows Phone 8 phones starting this summer.

I've asked Microsoft officials when they expect the final version of the Windows Phone Remote Desktop app to be available and whether they have plans to add support for Windows Phone 8. No word back so far.

Update: Windows Phone Remote Desktop will not support any versions of Windows Phone earlier than 8.1, Microsoft officials confirmed. The final version will be available by the end of this year, they added. And while Remote Desktop Gateway support is not currently part of the preview, Microsoft is not saying whether this feature will remain unsupported by the time the final ships. (But since the Remote Desktop app for Windows does support Remote Desktop Gateway, I'd say there's a strong likelihood the Windows Phone 8.1 version ultimately will, too.)

Windows Phone 8.1 adds a number of enterprise-focused features back to Microsoft's phone OS. Enterprise VPN, supporting IPsec and SSL VPN gateways; enterprise Wi-Fi; certificate management; S/MIME support for secure email; the ability to lock down documents in OneDrive via information-rights-management software and policies are part of the release. Some of these features require users to provision via a mobile-device-management product/service. But some others, such as EAP authentication for WiFi, also can be manually provisioned and configured.

Update: Several users are reporting that the Remote Desktop app for Windows Phone appears to be a universal app, in that it recognizes that they have already downloaded the Windows version, and that they simply need to "reinstall" the WP one.

(Thanks to Robert Brand for the tip on Windows Phone 8.1 Remote Desktop's availability.)