In Outlook Express (but similar in Oulook, as I recall using on another PC fairly recently; maybe wrong) . . . . . . . . . .
Don't bring up blank new e-mail page, but go to Address Book icon and bring up list of contents > Edit (on top toolbar) > Select All > Tools > Action > Send Mail.
This will automatically bring up a new blank e-mail page with all the addresses selected neatly in the "To:" header. ...Complete message and send.