IIS 6 SMTP service not delivering mail

Tags:
E-mail applications
Microsoft Exchange
Hi I have an IIS 6 SMTP service running on a W2k3 server. I am selectively unable to deliver mail to cetain domains. Looking at the packets these servers seem to use RFC 3030 and use BDAT to send data, rather than DATA. Instead of sending the body after the RCPT TO command, I either drop off or send the BDAT END command instead of the message body. I either get "semaphore timeout" errors or "the connection has been dropped". Any ideas?

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Two things I would try first. One, go to the SMTP properties and click on the Delivery tab. Click on Advanced and then click the configure button. Type in two or three external DNS servers. Second, make sure you have a reverse DNS record set up by your ISP. I mostly had trouble sending emails to the AOLs, Earthlinks, etc of the world. I found an article stating that the DNS resolution should be done by external DNS. I can’t remember why at this point but once I made the chance I did not have any further problems. Reverse DNS goes without saying as to why you should have it setup.

A lot of connection issues have to do with larger ISPs setting up security settings in attempts to thwart spam.

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  • MCScrapE
    Crap. The key part of the message just sunk in. My previous suggestions were for an Exchange server. You can certainly try a reverse DNS as many ISPs are now doing reverse DNS lookups for incoming email. While you can't configure the SMTP service to use external DNS you could possibly have the server this service running on have its DNS server entries set up for external DNS servers.
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  • Cptrelentless
    Yes, the solutions I've seen for this are Exchange based and I have a lot fewer configuration options to play with. I have reverse DNS externally available but I have two records (different service aliases). I was using the one that comes up second which may be the problem but it was still legal. I'll give this one a whirl. Reverse DNS was certainly a suspected cause. I was just trying to make sure it wasn't a known issue as we are only just starting to use 2k3 server and I have always been wary of un-service packed MS products.
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  • Cptrelentless
    Hooray! Hair pulling over. It was reverse DNS and it was because the first record was the one coming up and not the one I was using.
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  • Cptrelentless
    Actually, it seems that this was just one problem. The reverse DNS was preventing one of the work arounds from being successful. This was a work around I had picked up where you create a remote domain for the destination (company.com) and force it to use HELO instead of EHLO in its properties. This stops the server from using RFC 3030 and sends it the old fashioned way. This looks like a bug to me.
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