Is it poss to set up my Yahoo mail account so that the 'reply' email address doesn't show my yahoo.co.uk adres

I was hoping to route my company emails through my new yahoo email account but it seems that I am unable to 'mask' the fact that it's a Yahoo email account rather than a 'true' .co.uk domain name. It would be great if someone could advise me how to fix this - I had exactly the same problem with MSN but friends tell me that this is definitely possible