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550 ... Host unknown

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550 ... Host unknown - 16.Sep.2003 4:03:00 AM   


Posts: 1
Joined: 16.Sep.2003
From: USA
Status: offline
Hello All:

I have setup Exchange 2003 and am not able to receive inbound internet mail - sender receives NDR 550 <user@domain.com>... Host unknown (Name server: servername.domain.com.: host not found).

ISP has setup MX & Host records, same on Exchange server. Can send outbound via POP3 or SMTP, but can not receive mail directed to Exchange server as noted above.

Any suggestions, I am not an Exchange wiz, so any comments would be helpful.

JHM "[Confused]"
Post #: 1
RE: 550 ... Host unknown - 3.Oct.2003 3:56:00 PM   


Posts: 3578
Joined: 21.Jul.2001
From: W Yorks, England
Status: offline
Sounds like a problem with DNS somewhere. Set up a free mail account (Yahoo, Hotmail) and try sending some test mail and see what happens.
Also use NSLookup to check dns setup.

(in reply to WSTJNK)
Post #: 2
RE: 550 ... Host unknown - 7.Oct.2003 5:48:00 AM   


Posts: 72
Joined: 12.Aug.2003
From: Bogota
Status: offline

When you send messages to a remote domain that does not allow relay, you may receive an non-delivery report (NDR) similar to the following:
The following recipient(s) could not be reached:

User@Remotedomain.com on 1/6/00 7:58 PM

The originator does not have permission to submit message
dns;Wsilver.com failed 5.7.1 smtp;550
5.7.1 Unable to relay for User@Remotedomain.com


The actual reason for the NDR is that the remote domain has prohibited the sending domain from relaying. The NDR can be misleading because it implies that it is a permissions problem with the sender. The Delivery Status Notification (DSN) error code is defined in Request for Comments (RFC) 1893 as "Delivery not authorized, message refused." For additional information about status codes forDelivery Status Notification (DSN) messages, click the article number below to view the article in the Microsoft Knowledge Base:

(in reply to WSTJNK)
Post #: 3

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