two kinds of outgoing messages in Mail?

I’m trying to write a script (with no GUI scripting if possible) to send out all messages in the Drafts mailbox and i ran into a strange problem. If a new outgoing message is opened by double-clicking a message in the drafts mailbox or clicking on the “new message” button , apple scripts doesn’t want to send it using send command. It also doesn’t return any of its properties.

For example, the following gives an error

tell application "Mail"
set x to outgoing message 1
send x
end tell

Are there two kinds of outgoing messages? I can’t find anything helpful in the Dictionary.