In message <Pine.NEB.4.02.9808211426570.24658-100000@duhnet.net>, Todd Vierling
 writes:
>: 554 MX list for bar.com.pl.  points back to foo.bar.com.pl
>: 554 <user@bar.com.pl>... Local configuration error
>
>Add "bar.com.pl" to /etc/sendmail.cw and _restart_ sendmail.

Except that the default sendmail.cf does not set Fw/etc/sendmail.cw...

You'll need to either add "bar.com.pl" to the Cw line in sendmail.cf,
or add 'Fw/etc/sendmail.cw' and _then_ add "bar.com.pl" to /etc/sendmail.cw.