Thunderbird can't be set default mail client

[Mario Limonciello]

Binary package hint: thunderbird

Thunderbird asks me every time I open it if I want it to be the default. I say yes, but it doesn't take effect. I check Gnome preferred applications and it only lists Evolution. I check the unity panel button and the Check mail button opens evolution too

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: thunderbird 3.1.9+nobinonly-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-7.38-generic 2.6.38
Uname: Linux 2.6.38-7-generic i686
Architecture: i386
Date: Fri Mar 25 00:23:13 2011
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-dell-lucid-une-20100427-1
InstallationMedia: Ubuntu 10.04 "Lucid" - Build i386 LIVE Binary 20100427-14:29
ProcEnviron:
 LANGUAGE=en_US:en
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: thunderbird
UpgradeStatus: Upgraded to natty on 2011-03-02 (23 days ago)