set emailList to {}
tell application "Address Book"
set thePersons to get every person of group "Work"
repeat with aPerson in thePersons
set end of emailList to the value of aPerson's email
end repeat
end tell
tell application "Mail"
set theMessage to make new outgoing message with properties {visible:true, sender:"me.somewhere@rainbow.com", subject:"Testing", content:"Just testing Mail with Address Book"}
tell theMessage
repeat with anItem in emailList
repeat with anAddressItem in anItem
make new to recipient at end of to recipients with properties {address:anAddressItem}
end repeat
end repeat
end tell
end tell