Comment 10 for bug 540953

for additional bonus points :-)

add to the [Desktop Entry] group in /usr/share/applications/thunderbird.desktop

X-Ayatana-Desktop-Shortcuts=Compose;Contacts

then add underneath the translations

[Compose Shortcut Group]
Name=Compose New Message
Exec=thunderbird -compose
OnlyShowIn=Messaging Menu

[Contacts Shortcut Group]
Name=Contacts
Exec=thunderbird -addressbook
OnlyShowIn=Messaging Menu

then edit evolution.desktop in ~/.cache/indicators/messages/seen-db.keyfile to read thunderbird.desktop

hey presto additional menu items in one group without needing additional launchers :-D