Inbound mail to blocked: Spamhaus “open resolver” return code

[artbrut]

What type of hardware are you using: Virtual machine
What YunoHost version are you running: 12.1.36
How are you able to access your server: The webadmin
SSH
Direct access via physical keyboard/screen
Are you in a special context or did you perform specific tweaking on your YunoHost instance ?: no tweaking

Describe your issue

Hi,
we have the issue described several times here within the forum (and I partly can hardly read because my french is lousy). Some incoming mail to us is blocked. The sender gets the following message:
Service unavailable; Client host [IP] blocked using
zen.spamhaus.org; Error: open resolver;
I did comment the file /etc/postfix/main.cf

reject_rbl_client zen.spamhaus.org

but I 'm not sure if this is a workaround fixing my issue and the second question is: Is there another way to fix this?

Thanks in advance!

Share relevant logs or error messages

Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 89.234.141.66#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 185.233.100.101#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 185.233.100.100#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 2a00:5881:8100:1000::3#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 2a0c:e300::100#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 2a0c:e300::1337#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 2001:1608:10:25::9249:d69b#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 194.150.168.168#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 2001:1608:10:25::1c04:b12f#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 2a0c:e300::101#53
Dez 03 13:10:23 dnsmasq[1168]: Benutze Namensserver 45.67.81.23#53

[Aleks]

Could it be that you’re running an OVH VPS with IPv6 ?

Also please double-check that the postfix conf is up to date using yunohost tools regen-conf postfix --dry-run --with-diff

[artbrut]

Not OVH, but another Hoster where we have a Yunohost virtual machine and yes, we run IPv6. The output of the command (see that I commented the zen.spamhouse.org list)

yunohost tools regen-conf postfix --dry-run --with-diff
Warning: The configuration file ‘/etc/postfix/main.cf’ has been manually modified and will not be updated
postfix:
applied:
pending:
/etc/postfix/main.cf:
diff: @@ -129,7 +129,7 @@
permit_mynetworks,
permit_sasl_authenticated,
reject_rbl_client bl.spamcop.net,
-# reject_rbl_client zen.spamhaus.org

reject_rbl_client zen.spamhaus.org,
permit

Requirements for the HELO statement

• status: modified

[Aleks]

Also can you confirm that grep nameserver /etc/resolv.conf returns (only) 127.0.0.1 ?

[artbrut]

yes, it returns 127.0.0.1 (only)

[artbrut]

Hi, is there any further advice/ideas what I could do? (Apart from commenting zen.spamhouse.org in postfix config?)

[djizeus]

I am facing the same problem since today. I seems it appeared today when I upgraded the yunohost package from 12.1.27 to 12.1.36, I don’t know if this is a coïncidence.

My server is a bare metal rented to OVH, and it does use IPv6. grep nameserver /etc/resolv.conf returns only 127.0.0.1

I commented the spamhaus line in main.cf, thanks @artbrut for the tip.

[chatcannon]

I also had the same problem, and commenting out the spamhaus line in /etc/postfix/main.cf fixed it (at least temporarily)

[Edit by @Aleks : it’s not a good solution and is equivalent to removing the antispam mechanism entirely…]