[exim] domain refuses all mail sent from <>, dialup exim4/de…

Hi,

I have my Debian Sarge 3.1 dialup Box running Exim4 which forwards all
of my mail to my ISP's smtp host. Outbound mail works to some extent,
but as this message will probably illustrate, I believe my headers may
not be completely clean. Further, some destinations seem to receive
my email satisfactorily, while others just drop the email with no
bounce messages. After contacting sourceforge.net about some lost
email, a sourceforge admin sent me the following hint:

In this case, your domain refuses all mail sent from <>, the null
or bounce sender. This causes problems and goes against the SMTP
standard.

However, I am not sure whether the domain refusing all mail sent from
<> is my dialup Linux box or my ISP's smtp server. Is there some
configuration option which I need to properly set in the
/etc/exim4/exim4.conf file to fix this problem?

I read through the FAQ and Exim 4 Spec but I am still not sure whether
the problem resides with my box or the ISP. If its my box, how do I
set parameters in the exim4.conf file to solve the problems?

Thanks for any assistance.

marc

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