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#5.5.0 There was a SMTP communication problem with the recipient's email server  smtp: No email accepted from this host

mrfoofoo asked
Medium Priority
Last Modified: 2008-02-01
Perhaps someone can help me with this. We have no trouble receiving external email. But we are receiving the above NDRs on some, but by no means all, of the domains to which our Server 2003 SP1 Exchange 5.5 sends email. That is if the email ever makes it off the server, which I suspect many don't.  Certainly the Queue in Exchange shows many stuck there, generally with the message "SMTP could not connect to any DNS server".

At least 2 of the unreachable recipients have white listed our company.  We are only blacklisted as an open-range address at SORBS, which I cannot fix as the IP addresses listed belong to our ISP. Our Active Directory in Server 2003 was set incorrectly, specifying .net as the default SMTP address instead of .com, but I have fixed that.  Recipient policy is also @.com, I have unchecked .net .

Our mail server is mail.pfgoptics.com and is hosted by a third party provider, not our ISP. But our POP 3 connectors list the correct mail server address, and are having no problem retrieving email.  Our Default SMTP connector uses DNS. I have changed the FQDN in the virtual SMTP server to both mail.pfgoptics.com and mx.pfgoptics.com, and probably every other variation you could think of, to no avail.  I have done the same with our internal MX record. If you search on that at dnstuff.com, it comes up with mx.pfgoptics.com, rather than mail.pfgoptics.com, as our mail server, I have tried to reflect that in DNS but no combination works thus far …

I have also tried creating a separate SMTP connector using the ISP mail.pfgoptics.com address instead of DNS, listing the problematic sites and applying reasonable costings, also to no avail.  As emails were now showing a valid domain as unreachable, I deleted that. Also DNS related, I have checked that both the internet NIC and the Internal Network NIC reference the internal network address only for DNS. The Internet NIC uses a static IP address, not DHCP.

I have opened port 25 on the firewall to all protocols, SMTP not being listed explicitly, but, also no joy.  Adding a filter enabling SMTP also does not help.

I have run the Internet connectivity wizard twice - which necessitated restoring AD entries back to .com for SMTP afterwards - but did not fix the problem.

The elephant is the room is that, after fixing Active Directory entries, most sites were receiving, but upgrading our anti-spam software to enable real-time blacklists appears to have broken something again. White listing domains there was no help, nor was removing RBL protection, which I turned back on. I also stopped the anti-spam software, which has not improved the situation.

Any help would be most appreciated. I am offering 500 points as I have been banging my head on the server door for far too long now!

Watch Question

You have a major problem.
Who configured you DNS records?

You have

pfgoptics.com. MX IN 3600 mx.pfgoptics.com. [Preference = 30]

mx.pfgoptics.com. A IN 3600
mx.pfgoptics.com. A IN 3600
mx.pfgoptics.com. A IN 3600
mx.pfgoptics.com. A IN 3600
mx.pfgoptics.com. A IN 3600
mx.pfgoptics.com. A IN 3600

Who configured 6 A host records. Each A host reocrd has a differnt ip address.
Why do you need 6 A host records.

Futhermore your host mail.pfgoptics.com is pointing to a completely differnt ip address.
mail.pfgoptics.com. A IN 3600

Here is what you got to do. find out exactly which ip addrss is really the public ip address for your mail server. Delete 5 of A host reocords and keep only one A host record.

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Thanks for the info.  I do know the IP address for our 3rd party hosted mail server is  But looking at the A records in DNS, I only see the 192 numbers for the internal network.  I don't see where I could delete any 65 numbers on our server - they seem to be on the 3rd party parent server, which is web2010.com

Should I delete the 3 A records on our server with the internal number, leaving only the MX record referencing mail.pfgoptics.com (it currently references pfgoptics.com)?  Or contact web2010 and have htem adjust their mx records?

The only DNS record explicitly pointing to mail.pfgoptics.com is a PTR record in the reverse lookup zone.

I apologise for the repost, I am a bit of a neophyte in DNS.


It turns out we did have an incorrectly added MX record on our Server, redundant as we do not host our own mail server! We also made some changes to our DHCP entries in addition to the corrections to the DNS entries, which now point to our local server.  We did ensure mail.pfgoptics.com remained referenced in the PTR records of the Reverse Lookup in DNS. The SMTP connector was also tweaked, with mail.pfgoptics.com as the FQDN, pfgoptics.com as masquerade and our ISP as the smarthost.  We also added the ISPs external DNS servers to the external DNS list.

We did not change any of the above external MX records. I'm still not sure who actually configured them.  But as DNS was the main source of our woes, I am more than happy to award the points!
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