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"communications failure"

By david ·
Exchange 5.5 SP 3. Windows NT SP 4.

Trying to send e-mail to two different domains. flash.net and texas.net. When anyone in our office tries to send to these addresses they get a NDR:
"Unable to deliver the message due to a communications failure" We can send to any other domains. We have looked in Exchange Admin and there are no message filters. We have also looked in DNS Admin and cleared the cache. If I use my personal e-mail through my ISP I can send e-mail to flash.net and texas.net. We even opened the firewall to let all traffic through to and from our Exchange server. Any ideas?

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"communications failure"

by dmiles In reply to "communications failure"

I think this may have something to do with the proxy server setings with both flash.net and texas.net

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"communications failure"

by david In reply to "communications failure"
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"communications failure"

by labull In reply to "communications failure"

I have several sites I'm having the same problem with. Those sites have multiple MX entries as do flash.net and texas.net. Check the event viewer for multiple error 3011 - connection refused messages.

Our work around is to find which IP address points to the "real" mail server. You could use Telnet to check.

Then in Exchange Admin -IMS properties - Connections - E-Mail Domains - add the domain and IP address. Stop and re-start the IMS and it should work for you.

Let us know if it works.

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"communications failure"

by david In reply to "communications failure"

FYI

Turns out the Exchange server was setup to reroute all incoming SMTP mail. Someone was bouncing mail off our server. Flash.net and Texas.net use a service called MAPS RELAY SPAM STOPPER. They were blocking our IP. We fixed the vulnerability on our side and they stopped blocking us. Go figure....

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