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I am unable to send emails (email is send but never delivered) using OWA, from different remote locations using different ISPs. When I send emails from these remote locations relaying over available ISP, emails are being sent just fine.

Where should I look for problems in Exchange settings

  • accepted domains
  • send connectors
  • receive connectors.

Checking the message queue I have found the following error message

The message has been queued on server 'server.domain.local' since 2/26/2012 11:57:47 AM. The last attempt to send the message was at 2/26/2012 12:05:29 PM and generated the error '451 4.4.0 Primary target IP address responded with: "451 5.7.3 Require basic authentication." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.'.

What could cause this problem?


share|improve this question
@RobMoir I have double-checked the issue, and I can confirm that no emails that are sent to external email address are going through. (both from organization or from remote locations!). – John Feb 26 '12 at 12:34
emails are being sent between owa users. but no external emails are going through. – John Feb 26 '12 at 13:06
Then I would check the configuration of the Internet-facing SMTP connector. Without knowing your topology, what servers you have and what roles are installed upon them, etc. its difficult to be more specific – RobM Feb 26 '12 at 13:22
Yes, the problem was smtp connect. But what I do not understand is when I have more then one connector, how can I configure what connector gets used and when? – John Feb 26 '12 at 14:49
I'm going to try and convert my comments and some new thoughts into an answer. Sorry if it seems to repeat a lot of the comments, I'm trying to make some troubleshooting steps that might help anyone new who finds this, as well as help you. If my new comments still don't help, then more information about how exchange is deployed here would be useful. – RobM Feb 26 '12 at 22:47

The first question is where does the failure appear? Inside the exchange organisation or in emails sent outside the organisation? So the first question is does the error appear for internal emails, external emails, or both? OWA is obviously an exchange component in its own right, and so the emails are accepted by the exchange system the moment you click send, so we can assume that you've got a basic working system of some kind set up.

For external emails, as you say this is where the problem lies, I'd be looking at the SMTP send connector(s) for the organisation. You've got a box installed with the exchange hub transport role, and you might have another box configured as an edge transport server.

So the question is do you have an edge server? And what queues are showing issues? Are you using the default address space scope/ email routing? Are you using a smarthost? Is there a firewall between any of these servers? This is where I would start digging for the problem.

share|improve this answer
We dont have edge transport server. Basically the main problem is understanding the difference when sending emails using Exchange authentication or relaying over ISP with ISP username and password. I find it difficult to understand who uses which send connector? – John Feb 28 '12 at 19:31
Ok. If I understand what you're saying, you want to send your emails to the outside world via your ISP. You would configure a standard SMTP send connector for Internet use, and configure it to connect to the ISP mail server in a smarthost configuration. Its fine to have more than one SMTP connector configured on a system, each doing different jobs, if thats what it takes. – RobM Feb 28 '12 at 19:36
By different jobs you mean configure routing based on a difference address space. What happens if two connectors use the same address space? What is the benefit of using smart host over MX records? – John Feb 28 '12 at 20:37
1. Yes. 2. IIRC it then looks at costing for those routes (generally you wouldn't do this for internet facing traffic unless you were doing something specialised). 3. This allows an ISP or specialist email provider to handle filtering of your outgoing email - for an ISP this might be a requirement for using email on their network, and for a specialist provider (e.g. mimecast, messagelabs) this + pointing your MX records at them and letting them forward incoming mail to you lets you spam check, virus scan and content filter incoming and outgoing mail. – RobM Feb 28 '12 at 22:40
But I believe that receive connector also influences outgoing mail, especially when using OWA remotely. Can you confirm this? – John Feb 29 '12 at 6:57

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