Hi, Recently we found that in our exchange 2003 server , for specific domain mails are stuck in que. At senders side we get following error as: Your message did not reach some or all of the intended recipients. Subject: test Mail Sent: 9/7/2011 11:35 AM The following recipient(s) could not be reached: xyz@recipientdomain.com on 9/7/2011 11:37 AM A critical function required for the transfer or delivery of the message was not supported by the originator of the report <MX01.senderdomain.com #5.3.3 smtp;500 5.3.3 Unrecognized command> All mails for this recipientdomain.com are stuck in queue they wont get deliver. However for all other domains mail flow is totally smooth. Please help me on this . Awaiting for reply. Thanks in advance. Mandar Bhosale.

Hi, Can you telnet to their mail server and run a helo? Are you sending the email in html, rich text or plain text format?

Hi Michael, Thanks for your reply. I tried to telnet to mx of destinationdomain.com. It gets connect. But If I type helo or ehlo it gives an error as 500 3.3.0 Unrecognised command. I tried to send html , rich text or plain text but still same behavior . Kindly provide your response. Awaiting for reply. Thanks in advance. Mandar B.

Hi Mandar, Above error code is mentioned as storage issue on remote domain server as per MS article.. Numeric Code: 5.3.3 Possible Cause: The Exchange 2000 remote server or the Exchange 2003 remote server is out of disk storage to hold mail. This issue occurs most frequently when the sending server is sending mail with binary DATA (BDAT). This code may also indicate an SMTP protocol error. Troubleshooting: Make sure the remote server has sufficient storage to hold mail, and examine the SMTP protocol log for errors. Is this issue appearing for few domain or single domain? If single domain, contact remote domain user or admin. Thank you.

Can you send to this domain from an external account like hotmail? Sure there isnt an issue at thier end "Numeric Code: 5.3.3 Possible Cause: The Exchange 2000 remote server or the Exchange 2003 remote server is out of disk storage to hold mail. This issue occurs most frequently when the sending server is sending mail with binary DATA (BDAT). This code may also indicate an SMTP protocol error" - http://support.microsoft.com/default.aspx?scid=KB;EN-US;284204 Sukh

Hi Rajkumar, Thanks for your help. I have confirmed that If I try to send mail to same destination address using other doamin such as hotmail or something else then it get properly deliver. This issue lies between our sending doamin to that specific recipient domain only. Kindly guide me about to check anything at my server end. Awaiting for your reply. Thanks in advance. Mandar B.

Hi Mandar, There is no problem at your end, kindly contact the person over phone, to whom you are sending email and getting error. Ask him to contact the Exchange admin over there and inform the issue to him. He will take the neccessary step. There is no problem at your end. Thank you

Have you checked to see if youre domain isnt being blocked by the receivers end? Is is blacklisted? Sukh

Check the domain if its black listed under www.mxtoolbox.com also check does your reverse DNS is functioning properly. In most cases if the RDNS doesnt work properly chances are like external emails doesnt relay. Vinod

Do they or your domain have SPF running? or the provider?