[Exim] MAIL FROM: troubles

hello,

I have a small network connected (non-permanent/dial-up) to internet through the gateway (which act as a
mail-hub too, it recieve mail from local network and send it to upstream server). Also i have
local nemeservice in my network (domain *.local). 'Cause of it i have MAIL FROM:<myname@???> in
the request to remote server. Such request fails ... remote server claims:
"Host host.local cannot be looked up"
This problem may be solved by setting up primary_hostname option to fake host (which realy exists), i
think it's negative way. How can i place in MAIL FROM my real mail address ?

thanks in advance
blackOut

p.s. gateway, upstream server and local workstations are exim powered