sender: field shorter?

I am getting used to exim. Would it be possible to optionally set
this field to

sender: user@site

rather than

sender: gecos_data <user@site> ??

It seems an extra password lookup to find this information which IMHO is
not needed.

Thanks.

BTW I think the documentation is very good.

--
Alan Thew                                       alan.thew@???
Computing Services,University of Liverpool      Fax: +44 151 794-4442