Setting sendmail not to resolve domains?

[Dragoncrest]

	Hi all. I'm wondering how I would go about disabling dns lookups in 
sendmail?  Right now it's denying mail delivery because it can't resolve 
the senders domain of most of the mail it's recieving.  I'd like to tell it 
to just accept them regardless if it can resolve the domain name or 
not.  Can someone tell me where and how to do this?  Maybe give me some 
examples?  Thanks. Also, I'm a sendmail newbie so please keep it as simple 
as possible.  Thanks.