MS and Postini (Google) are in a tizzy, and long story short, Microsoft was/has blocked Postini's IP block. I think it's been lifted again, but my workaround isn't working (see below).

I have a Small Business Server with Exchange 2003 SP2 on it and the default SMTP connector is setup to route mail through Postini as a smarthost. This works fine. Address space is:

* cost 1

Because of this blockage, I created another SMTP connector called "Microsoft Domains" set to use DNS to deliver mail for the entire organization. Under the address spaces, I have the following:

hotmail.com cost 1
msn.com cost 1

I have only one SMTP Virtual Server (the Default one) as a local bridgehead for both of these connectors; under Delivery -> Advanced the smarthost field is empty.

The issue is that my "Microsoft Domains" connector seems to be ignored -- I sent a test email to my hotmail account and expected to see my WAN IP in the "Received By" field in the headers, but it's always from Postini's block ( Further more, I'm still getting 5.3.3 bounce errors from Microsoft's mail servers when I send to the hotmail.com account, so it's definitely still going out Postini's smarthost:

5.5.0 smtp;550 SC-002 Mail rejected by Windows Live Hotmail for policy reasons. The mail server IP connecting to Windows Live Hotmail has exhibited namespace mining behavior.

The TechNet documentation implies that the connector with the most specificity will "win", but this doesn't seem to be the case:

The address space defines the mail addresses or domains for the e-mail messages that you want to route through a connector. For example, an address space of * (asterisk) encompasses all external domains—this connector is used to route all external e-mail. If you created a second connector with an address space of *.net, Exchange would route all mail sent to a domain with a .net extension through the second connector. This action occurs because Exchange selects the connector that has the most similar address space. This setting is configured on the Address tab of the SMTP connector's properties.

I've tried restarting the Exchange Routing Engine service but to no avail; I've tried changing the cost of the default connector to 5; I've also tried this on an SBS 2008 Exchange 2007 box, but no dice. Any ideas?

2 Answers 2


I'd tweak the costs myself:

"If you have multiple connectors, especially a connector that has a * in the address space (for sending email via your ISP) then you need to adjust the cost carefully. The wildcard SMTP connector with the * should have the highest cost, SMTP Connectors pointing to internal servers should have the lowest (so that they are used first). If you want to load balance the connectors then you can set multiple connectors at a cost of 1."

So I'd raise the cost of the postini connector to 2 so everything tries the Microsoft Domains connector first and then when it notices the specific address space goes to the postini connector.

  • Ok I'll give that a shot.
    – gravyface
    Feb 19, 2010 at 14:46
  • That was it. Thanks so much! Curious though: where are you quoting that text from?
    – gravyface
    Feb 23, 2010 at 17:59

Can your Exchange Server resolve the Microsoft domains? Exchange uses DNS to resolve domains before they are categorised,

Sending Internet Mail To send Internet mail, Exchange relies on the same components that it relies upon for receiving Internet mail: DNS, the SMTP protocol, the message categorizer, the advanced queuing engine, and the Exchange routing engine. Internet mail is sent through Exchange in the following manner:

1.An internal user sends a message to a remote domain. The message is submitted on the Exchange server on which the user's mailbox resides.

2.The message is submitted to the advanced queuing engine in one of two ways:

If the message was sent using a Microsoft Office Outlook® Web Access or Outlook (MAPI) client, the Exchange store submits the message to the advanced queuing engine through the store driver.

If the message was sent using a Post Office Protocol (POP) or an Internet Mail Access Protocol (IMAP) client, SMTP passes the message to the advanced queuing engine.

3.The message categorizer then queries the global catalog server with the recipient address to find the user. If the recipient address is not in a recipient policy, or if a matching recipient with a proxy address does not exist (the recipient address will not be stored in Active Directory), the message categorizer determines that the message is bound for a remote domain.

4.The advanced queuing engine calls into the Exchange routing engine to determine the next destination, or hop, for a route to the address space that more closely matches the remote domain.

5.With this information, the server determines whether to send the message, to route it to the smart host, or to use an SMTP connector with the remote address space.

6.If there are multiple connectors or virtual servers that handle outbound mail, the advanced queuing engine determines the virtual server or connector with the address space that most closely matches the address space of the remote domain and any restrictions for that connector.

7.The message is routed to the outbound connector's SMTP virtual server or to the outbound SMTP virtual server that is responsible for delivery.

8.The SMTP virtual server located on the Exchange server that performs categorization then uses its metabase information for the route action attribute for the remote domain.

9.The SMTP virtual server on the Exchange server then performs one of two tasks:

Uses DNS to look up the IP address for the target domain and then attempts delivery of the message.

Forwards the message to a smart host that assumes responsibility for the DNS resolution and delivery.

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