Dear Vaibhav
You will find a macro L in sendmail.cf which is used to forward the unknown message to other destination. Configure it as below DLesmtp:NameOfTheUsDomain If you use sendmail.mc file to create sendmail.cf then add below line in sendmail.mc and recreate sendmail.cf define(`LUSER_RELAY', `esmtp:NameOfTheUsDomain')dnl
Regards, Bilal Ahmed Mazhar