Yes, the week has only just begun and already we have a new beta build to play with. The latest beta refresh of Mail Desktop (Build 1034) includes:
- Virus scanning of attachments
- Photo Emails can be sent via POP accounts
- RSS syncing - the ability to sync all your RSS feeds at once
- Autoupdate - now you can opt-in during setup to receive update notifications through Automatic Updates
- Contact Import improvements – any suspected duplicate contacts are identified and can be merged into one
- Performance improvements, especially around signin
- Over 1000 issues fixed!
Download now (15.5MB)
This build appears to have much improved Vista support (it now logs on), something which will undoubtedly please the legions of Vista testers out there. If you have Automatic Updates disabled before you install this build, you will want to disable it again via the Control Panel once you have completed the installation
We have a QnA with the team to hopefully be posted shortly :)
Update:Tanja from the Mail Desktop team has more information on the update.
Here are some screenshots for your viewing pleasure:
Setup
Setup 2:
Main Screen
Color Change
Sign In 
using Live ID,
Name/Password, or
OpenID
or
Join LiveSide
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