[CentOS] tail -f /var/log/maillog error

> I am ruunig a Mailserver (Sendmail) on RedhHat 9,
> 

I suggest you plan a migration to Centos 4.4 as Redhat 9 is ancient, its 
version of sendmail (have you at all updated that box?) is full of 
security holes and even if your sendmail has been patched against its 
security holes, the other stuff that comes with Redhat 9 is riddled with 
security holes.