[CentOS] Email client shortcut

Under SL 4.x GNOME, when I assigned a button shortcut for Email (the "Mail" button of my Microsoft Internet Keyboard), the default email client (thunderbird) was launched.

Under CentOS 5.0, Thunderbird is launched as "thunderbird -compose %s" (defined in GNOME "Preferred applications"). This has as an effect when I press the email shortcut a compose new message window opens, and not the thunderbird main client. If I erase the "-compose %s" part, it has as a side effect that when I click on an email web link under firefox, it doesn't open the compose window but the thunderbird client. Any nice fix on this, other than choosing between the two?

Thanks.