Hi to all We r running Exchange 5.5 which is ESMTP enable. Some users r sending mail to a particular domain and getting NDR saying send hello first. i have try to investigate the matter and telnet on 25 port of that domain and found that it is not recognizing EHLO command which is default ESMTP command. thats why all mails r bouncing back. Other side they r using Exchange 2000. I wana know how we can resolve this issue. I dont want to disable my ESMTP. what other setting can be done on other end so that they can accept EHLO command. I guess they r using some firewall or SMTP Gateway.