The "Check Email" shortcut launches Evolution even though Thunderbird is set as Preferred Mail Reader

[fishears]

Binary package hint: unity

Description: Ubuntu Natty (development branch)
Release: 11.04

unity:
  Installed: 3.8.4-0ubuntu1
  Candidate: 3.8.4-0ubuntu1
  Version table:
 *** 3.8.4-0ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ natty/main i386 Packages
        100 /var/lib/dpkg/status

I click on the Ubuntu Icon (top left) and the Search & Shortcuts Lens appears. Click "Check Email" and the system launches Evolution. I have Thunderbird installed and set as my Mail Reader in Preferred Applications so I would expect Thunderbird to be launched rather than Evolution.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: unity 3.8.4-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-8.41-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
CompizPlugins: [core,bailer,detection,composite,opengl,decor,regex,gnomecompat,mousepoll,snap,place,wall,animation,resize,compiztoolbox,grid,vpswitch,move,workarounds,imgpng,expo,session,ezoom,staticswitcher,fade,scale,unityshell]
Date: Sat Apr 9 09:31:48 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha i386 (20110302)
ProcEnviron:
 LANGUAGE=en_GB:en
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: Upgraded to natty on 2011-03-26 (13 days ago)