We are currently in the beginning stages of migrating from Exchange 2003 to Exchange 2007. We have got to the point where internal mail between the two systems is working perfectly with all of our testing accounts, the problem is now that Exchange 2007 is not able to send email to external domains.

Seems like an easy enough problem, I've googled it read many articles that have all said the same thing. Create an Internet Send Connector with an address space of '*' and a cost of '1', use domain name system '(MX)' records to route mail automatically.

After reading through that on so many different sites including technet I finally went ahead and did just that. I sent an email to an external address from one of the testing accounts and it didn't make it. I went and checked the mail queues on the hub server and the Unreachable queue had several hundred other messages in it! All email destined for the Internet from the Exchange 2003 side started trying to get out through the Send Connector which still couldn't send to the internet.

I disabled both the Windows Firewall and the Anti-virus in case one of them was preventing the mail from getting sent, and the Unreachable queue kept growing. I deleted the Send Connector and after a few minutes mail started routing out to the Internet as normal.

There was only two other thing that I thought might be going wrong. I checked using nslookup that the domain were resolvable by the server, and manually connected to the remote SMTP servers from the server using telnet to verify that the connections could be opened, both worked.

The diagnostic tools built into Exchange 2007 told me nothing more than 'A matching connector can not be found' even with the * connector. I'm stumped can anybody help me?

  • Which client: normally connected Outlook, Outlook Web Access or a SMTP client (Outlook Express, Windows Mail etc.)? – splattne Jul 1 '09 at 17:43
  • This isn't a client issue, mail is being routed through the system. The problem is the server software (Exchange 2007) is unable to send mail outside of the active directory forest. – TrueDuality Jul 1 '09 at 18:23
  • yes, but Exchange handles relaying differently. see this for example: petri.co.il/… – splattne Jul 1 '09 at 18:36
  • Any mail traveling into the system, I've tested this with OWA, SMTP, and an Exchange 2007 client. The mail gets into the server, it's not being rejected when the client connects. The problem is that once it is on the server sending to the Internet is fine. Sending internally works perfectly. – TrueDuality Jul 2 '09 at 12:59

FIXED IT!! (well, at least on my server, not sure if your issue is the same)

It seems that Exchange 2007 does not automatically come with an external SMTP connector. This seems odd as I was able to send external email before setting up the connector to the exchange 2003 server but following the instructions below worked perfectly.


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  • Please read fully through the post, after creating the Send Connector all mail from 2003 gets routed to the 2007 half and 2007 still can not send mail to the internet. – TrueDuality Jul 2 '09 at 12:58
  • Strange, I don't see anything stating that in the article but its still early and I haven't had my coffee yet. I can confirm that both 2003 and 2007 servers can successfully send email to internet users though, it doesn't look like 2003 is routing through 2007 but that could be because of the 2003-2007 connector that shuffles internal email between the two. Now prior to this fix, 2007 was trying (and failing) to route ALL external email through the 2003 server. – drgncabe Jul 2 '09 at 13:15
  • I refer you to the second paragraph and first sentence of the third. – TrueDuality Jul 2 '09 at 15:17
  • Hrmmm, I see what your saying. Oddly enough, while all 2003 traffic is going out the lowest cost connector (the 2003-2007 connector) it is going out the Exchange 2007 internet SMTP connector without issue. So as it stands right now it goes Email->Exch03->Exch07->Internet. This is odd, and from what your saying it shouldn't work but that's the way the queues are flowing, I have no messages in the unroutable queue. What are your connectors on both servers? Also, have you tried the mailflow troubleshooter yet? Doubt it'll help but you never know. – drgncabe Jul 2 '09 at 19:47
  • I have tried the mailflow troubleshooter, unfortunately it doesn't tell me anything beyond that the mail is backing up in the Unreachable queue and that it can't find a matching connector (even with a * connector). It also seems that the mail on the 2003 side is still leaving through the 2003 connector, or at least until the send connector is created on the 2007 side. I've looked at all the connectors and they all have a cost of 1, so mail traveling to the internet from the 2003 side shouldn't cross over to the 2007 side anyways as that would be a cost of 2 rather than 1. – TrueDuality Jul 6 '09 at 22:08

Going back through my questions I realized this one was never answered. Turns out that not a single Exchange 2003 server had an explicitly defined send connector and were all using the default one. As soon as a send connector was explicitely defined within the Exchange Org all mail started using that.

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