Is there any way that i can enter all my companys clients emails in the exchange server 2007 so that it appears as one group, because we have to frequently send emails regarding the price fuel surcharges to the clients and BCC all of them. Thus making it easy for the staff to send such mails to the clients.Thanks

You'd have to add mail enabled contacts for their SMTP addresses then add the contacts to a group.

Isn't there any way that i can add many contacts easily at once.

create a CSV, an use the import-csv cmdlet piped to a new-mailcontact cmdlet