uhmm... a few clarifications to your post. People are here are Perl coders, not particularly CGI coders. Neither of which have anything to do with sendmail. And, you don't give enough information to even consider a fix.
My suggestion, if you're using a CGI script to send out the emails, would be to contact the author of the script (or post snippets of relevent code so we can see what's going on), otherwise consult sendmail manuals, or maybe even SMTP info.
In any case, I don't think Perl Monks is the place to get help for your problem.
-Syn0