1 Topic by echo5

  • echo5
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Topic: Mail blocked. Spamhaus "open relay" public DNS server blocking

I'm encountering an error that is wrecking havoc on my mailserver. I'm posting to ask if anyone solved this, and as a marker for others having the issue.

Spamhaus is now responding with error codes on lookups if your mailserver uses a public DNS server for address lookups. If you're server is using 8.8.8.8, 1.1.1.1, etc it may break postfix/amavis and spam rbl functions.

Spamhaus offers a DQS service if you signup that doesn't cough up the errors. Can be free if you're not commercial. Can't tell how to integrate it though.

Only solution I can see if running my own dns, which I don't want to do.

Are there any other solutions?

You'll see errors in /var/log/maillog like:

postfix/smtpd[21777]: NOQUEUE: reject: RCPT from mail-ot1-f41.google.com[209.85.210.41]: 554 5.7.1 Service unavailable; Client host [209.85.210.41] blocked using zen.spamhaus.org; Error: open resolver; https://www.spamhaus.org/returnc/pub/24 … ac46:d1d3;

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2 Reply by ZhangHuangbin

  • ZhangHuangbin
  • ZhangHuangbin
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Re: Mail blocked. Spamhaus "open relay" public DNS server blocking

echo5 wrote:

Only solution I can see if running my own dns, which I don't want to do.

How about run a local cache-only DNS server? not need to move your domain names to this local DNS server.

3 Reply by echo5

  • echo5
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Re: Mail blocked. Spamhaus "open relay" public DNS server blocking

ZhangHuangbin wrote:
echo5 wrote:

Only solution I can see if running my own dns, which I don't want to do.

How about run a local cache-only DNS server? not need to move your domain names to this local DNS server.

I moved to two different private DNS servers and it still fails. I had to edit /etc/postfix/main.cf and comment out the spamhaus RBL lines. It just stopped working, even with private DNS servers.