Problem with Bind & Sendmail

[Harvey, Deborah D.]

Hey,
> I have upgraded our bind to 9.1.1.5 and am running Sendmail 8.9.3.  We are
> now having a small problem with some of our mail.  Some mail is being
> returned.  The error we are getting is "sender domain must resolve".  We
> have checked and the domains are resolving correctly.  Has anybody
> experienced this problem before or does anyone have any suggestions as to
> why this is happening?
> 
> Thanks for any help.