OOT: Mail rejected with bogus helo

[Budi Febrianto]

Dear All,

I know this OOT, but because many sendmail experts in here, I give it a 
shot.

I'm using sendmail-8.13.8-2.el5 with MailScanner 4.65.3.

Whenever my users sent emails to certain domains, it will rejected with 
this error.

 >>>>>
553 yyy.yyy.yyy.yyy rejected due to spam, contact 555-505-5555 (bogus 
helo xxx.xxx.xxx.xxx)
 >>>>>

I'm not sure what happen, because I don't have the same problem with 
others domain.

TIA