Question : Microsoft SBS 2003 - Exchange Server. 551 Command RCPT User not local and relaying not permitted

Reporting-MTA: dns;sbs1.mydomain.com
Received-From-MTA: dns;opspc001
Arrival-Date: Thu, 20 Jan 2005 18:47:46 +0800

Final-Recipient: rfc822;[email protected].sg
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;551 Command RCPT User not local and relaying not permitted
from you (202.136.25.25)

I just took over from my ex-colleague on the exchange server (Microsoft SBS 2003) not long ago.  Since yesterday the users are not being able to send any email out to the outside world.  They keep receiving these delivery failure message.

My email and domain is hosted by other email hosting company.  However, the company having problem sending out large amount of emails(newsletter) through the current hosting company.  So the exchange server(SMTP) was purely setup to send out huge amount of email.  There is no user a/c in my ex svr.  

I know some ISP email a/c require "My outgoing server(SMTP) required authentication" to be configured in the ms outlook in order to send out the email.  But how do I go about it in my exchange?

My previous administrator also check the settings also can't figure wat went wrong suddenly.  Would be glad if anyone could help me on this.  Thx for the help

Answer : Microsoft SBS 2003 - Exchange Server. 551 Command RCPT User not local and relaying not permitted

Ok, if you are on a Dynamic IP, then you don't have proper Reverse DNS entries, your IP address is included on a number of blacklist for the express purpose that it is dynamic and you don't have proper MX records, there are a lot of site that just won't plain except email from you anymore. As SPAM continues to become a bigger problem, more people are implementing more controls against it. Unfortunately, it is affecting you with your outbound email. You need to either tell your clients to use the ISP for outbound, or contact your ISP about how to resolve this issue as I have laid out above.

Charles