2 questions on git-send-email usage

Hi

I'm wondering what am I supposed to answer when git-send-email
is asking me :

Message-ID to be used as In-Reply-To for the first email?

I'm running this command:

$ git-send-email --no-signed-off-by-cc --no-chain-reply-to --to foo@bar.com --compose /tmp/patch/

to write an introductory message, and all patches are sent as replies to
this introductory email sent.

I also noticed that git-send-email removes the commit message of each
patches I sent, I don't think this is the normal behaviour though. What 
am I missing ?

Thanks

Francis