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A business associate of ours out in China who we have been working with for over 5 years is now struggling to email us in the UK.. he is receiving the following error:

Your message to .... was rejected by the recipient domain. The error that the other server returned was: " SMTP error through SDN 40 error, RCPT TO: 553 Your IP [120.31.134.234] is on one or more DNS blacklists. ulc: 9223291036807641301, rcp: 0001. (#5.1.1)".

I understand from using mxtoolbox.com that the IP is on 3 blacklists.

Is there anything we can do about this on are side? It's important we can email him and he can email us.

Nathan Smith
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  • Can you confirm that it's a mail server that you control that says the *553 Your IP [120.31.134.234] is on one or more DNS blacklists. ulc: 9223291036807641301, rcp: 0001. (#5.1.1)* bit? If so, the answer is "Yes, most likely", but I don't think it's really possible to say much more than that without any information whatsoever about your setup. – Håkan Lindqvist Mar 30 '16 at 08:20
  • I am not too sure about our set-up. I believe OUR domain is hosted with http://internetters.co.uk/ ... we use Microsoft Exchange 2010, and we have AVG Cloudcare – Nathan Smith Mar 30 '16 at 08:27
  • The Anti-Spam components are disabled by default on Hub Transport servers in Exchange Server 2010, that's why it's disabled. You'll need to enable the Anti-Spam components and then configure your Allow List. - https://technet.microsoft.com/en-us/magazine/ff404233.aspx - https://technet.microsoft.com/en-us/library/bb201691(v=exchg.141).aspx - https://technet.microsoft.com/en-us/library/bb125225(v=exchg.141).aspx – joeqwerty Mar 30 '16 at 11:06

2 Answers2

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A quick dig says

:~$ dig +short -x 120.31.134.234
mail.globalmail.com.cn.

so it looks your business partner is emailing via an ISP. Most likely someone is spamming from that ISP and they're not handling it properly.

Blacklist operators usually provide a possibility to unlist domains/IPs that are (more or less) wrongly blacklisted. You can try that, with your result from MXtoolbox, or you can talk to your own ISP and have them do the same.

Other than that: Have your associate change ISP, or use GMail or the likes...

Cheers,

Anders R. Bystrup
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If you are using your own mail server, then you can whitelist 120.31.134.234. How to do that depends on the mail server you are using.

If your mail is hosted on an external provider's mail server, then you should contact your provider asking them to fix the problem. It is not unlikely that your provider is going to have lots of excuses blaming somebody else for the problem, you need to be prepared for that. Whatever excuse your provider may come up with, I would reiterate the simple fact that it is your provider who is rejecting legitimate emails and you want them to stop doing that.

If you cannot get your provider to accept these mails your last option is to switch to another provider.

If your business associate is experiencing this problem with other recipients as well, then they may have to do something about the problem from their end. But if you are the only recipient they have a problem with, then they can reasonably say the problem lies on your end, and you have to sort it out with your provider.

kasperd
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  • Many thanks for your reply. We use exchange? so I think it's our own mail server. I read online to go to Exchange management console, navigate to server config > hub transport > anti-spam and add the IP into the Allow List. My only issue now is that the Allow List is currently Disabled.. I am wary of Enabled it in case it's Disabled for a reason. – Nathan Smith Mar 30 '16 at 09:13
  • Fundamentally, though, your partner must fix his act. He did not end up on a blacklist by accident. Likely their server is ridiculously configured and an open relay. – TomTom Mar 30 '16 at 09:17
  • @NathanSmith I can answer questions about SMTP. I cannot answer questions about Exchange. That's a piece of software I have never touched and probably never will. – kasperd Mar 30 '16 at 10:28
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    @TomTom That is speculation which the OP won't be able to document towards their business associate. And there is no evidence suggesting that business associate is taking part in any abuse. Also as long as none of the contracts between the involved parties assign any authority to the blacklist in question, then you can't really use that blacklist as excuse for blocking *legitimate* emails. – kasperd Mar 30 '16 at 10:33
  • @kasperd Be a little smarter. You basically tell that the other side was put on a blacklist without any reason. That is ignorant. Blacklists have a reason to mark IP addresses as bad. yes, errors happen - which is why they also have rules how to lift this. A sensible approach starts with identifying the blacklist and looking up why. Likely some super competent admin was not aware what "open relay" means and thus got blacklisted. – TomTom Mar 30 '16 at 10:36
  • @TomTom That's *not* what I am saying. I am saying that unless the OP can document the legitimacy of the blacklist, it is the OP who is responsible for ensuring that the filter does not block *legitimate* emails. – kasperd Mar 30 '16 at 10:43