Dave Millen writes:
> It seems as if the problem lies within 'sendmail'
> 
> Is there another switch that I should set that will use the initial
> authorisation for all subsequent messages?

Sendmail uses no authorization, and it is unlikely that "sendmail" qua 
"sendmail" is the issue. Maybe you should try watching the interaction 
on the wire. tcpdump is your friend. :)

Perry