Outlook 2007. Send button greyed out

[robbieg]

A colleague has created some emails as drafts and sent them over to me as
attachments to a message for me to finish off and send to their destinations.

When I open these attachments, they open up fine into Outlook 2007 but if I
then type in the recipient address, the Send button is greyed out and I
cannot send the messages.
Outlook works fine except for this.

Any ideas?
thanks in advance.