Here's a list of pro's and cons on deciding to change to Thunderbird: https://blueprints.launchpad.net/ubuntu/+spec/desktop-o-default-email-client

Evolution pro's:

• Good integration with the desktop already (eg, messaging menu and appmenu)


• Integrated with existing translation infrastructure for developers in launchpad


• Calendaring functionality by default, and integrated with the desktop


• Support for syncing contacts with U1


• Contacts sync with GMail


• GNOME release process is better aligned with our 6 month cycle


• Exchange support (no idea how well this works, but it exists)

Evolution con's:

• Outdated and confusing UI


• Historically has been fairly slow and unstable (although it is better now)


• UI is pretty bad on netbooks and other small form-factor devices


• I'm not convinced that Evolutions additional features are that important to our target users

Thunderbird pro's:

• Responsive and more active upstream


• Familiar brand for users moving from other operating systems, which has the same benefits as shipping Firefox


• Lots and lots of extensions, and a very rich extension framework


• Initial account setup is so much more intuitive


• I like the tabbed interface ;)

Thunderbird con's:

• Translations not integrated with Launchpad (we have the same issue with Firefox though)


• Integration with the desktop lacking (no messaging menu or appmenu)


• No exchange support (not true for lightning: there is a working lightning data provider, http://gitorious.org/lightning-exchange-provider/pages/Home )


• Calendaring support is only available via an addon (Lightning), and is not integrated with the panel clock


• No GMail or U1 contact sync (although GMail contact support is available via an addon)

And adding all up the result is in favor of Thunderbird it seems.

Here is the the pdf 'Thunderbird & Evolution User research findings' on which they based the conclusion to change.

On canonical Thunderbird & Evolution Usability Testing