Do you mean to send a message that you've already written and is sitting in your outbox, or do you mean you want a button to create a new message?
To create a 'New Message' desktop icon/command that you can drag anywhere, right click on the desktop, new, shortcut. Type mailto: in the box, in the next box give it a name like 'new message' or similar, then click finish.
To create a 'New Message' desktop icon/command that you can drag anywhere, right click on the desktop, new, shortcut. Type mailto: in the box, in the next box give it a name like 'new message' or similar, then click finish.