0sg.net bouncing for bad reverse lookups?

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Re: 0sg.net bouncing for bad reverse lookups?

Postby skyrock » Wed Jan 18, 2023 9:29 pm

I still get the reverse DNS error. I host my own mail server and even restarted it.

Code: Select all
 dig +noall +answer ob.0sg.net
ob.0sg.net.             1800    IN      A       216.75.62.102


Code: Select all
dig +noall +answer -x 216.75.62.102
102.62.75.216.in-addr.arpa. 4439 IN     PTR     gourmet.spamgourmet.com.


Seemts to me the PTR entry is still wrong?
skyrock
 
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Re: 0sg.net bouncing for bad reverse lookups?

Postby geekciro » Wed Jan 18, 2023 10:32 pm

skyrock wrote:I still get the reverse DNS error. I host my own mail server and even restarted it.

Code: Select all
 dig +noall +answer ob.0sg.net
ob.0sg.net.             1800    IN      A       216.75.62.102


Code: Select all
dig +noall +answer -x 216.75.62.102
102.62.75.216.in-addr.arpa. 4439 IN     PTR     gourmet.spamgourmet.com.


Seemts to me the PTR entry is still wrong?


If it's the error we were seeing the other night, you need to check the PTR for *your* mailserver, not theirs.

If it's the other way around, and your mailserver is rejecting their RDNS lookup, that's a different issue (but the DNS results you posted shouldn't be an issue either way)
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Re: 0sg.net bouncing for bad reverse lookups?

Postby skyrock » Wed Jan 18, 2023 10:56 pm

Thank you, you are right, the server is complaining about my rDNS. It is properly set, I even checked it using mail-tester.com

The error message I get is:
Code: Select all
host gourmet7.spamgourmet.com[216.75.62.102] said: 550-X-Host-Lookup-Failed:
    Reverse DNS lookup does not match for 123.456.789 (deferred) (in
    reply to MAIL FROM command)


Mails also do not arrive when sent from a different mail provider.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby hausgeist » Wed Jan 18, 2023 11:27 pm

Looks better now, but still the usual volume is not back. Looks like some sending systems hold back sending due to the bounces. Interesting effect.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby skyrock » Thu Jan 19, 2023 5:11 pm

All mails to my spamgourmet addresses still bounce ;/ Am I the only one?
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Re: 0sg.net bouncing for bad reverse lookups?

Postby skyrock » Thu Jan 19, 2023 7:27 pm

According to a whois query spamgourmet appears to use the Namecheap DNS servers (dns1.registrar-servers.com & dns2.registrar-servers.com)

Could the problem be with these name servers?

Querying Google DNS and many other DNS returns a valid PTR record for my mail server's IP address:
Code: Select all
dig @8.8.8.8  +noall +answer -x MY.IP.HERE
-> valid record


Querying a namecheap DNS returns nothing:
Code: Select all
dig @dns1.registrar-servers.com  +noall +answer -x MY.IP.HERE
-> empty record
skyrock
 
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Re: 0sg.net bouncing for bad reverse lookups?

Postby LindaB » Thu Jan 19, 2023 10:03 pm

Darn! I'm not getting my spamgourmet emails, again. The most recent one that I got seems to have arrived four hours ago.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby isbbs.thebluecat » Fri Jan 20, 2023 11:57 am

Dear everyone,

It is the same for me.

Spamgourmet is not forwarding out to the email server configured any email that receives...
I hope the system is not destroying those emails and after the system is restored we will receive them.

How I can help to improve this situation?

Best regards and have a lovely day,

K
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Re: 0sg.net bouncing for bad reverse lookups?

Postby hausgeist » Fri Jan 20, 2023 1:45 pm

Issues ongoing for me too.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby pbb » Fri Jan 20, 2023 6:10 pm

I have received a number of errors this week, but I am still receiving them.

This one from this morning:

<............@dfgh.net>: host gourmet7.spamgourmet.com[216.75.62.102] said:
550-X-Host-Lookup-Failed: Reverse DNS lookup does not match for 66.111.4.28
550 (deferred) (in reply to MAIL FROM command)

[Edit] It looks like some mail to the dfgh.net address is getting through.

I have received two dfgh.net emails correctly, during the day.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby geekciro » Fri Jan 20, 2023 10:10 pm

Yup, stopped working for me, too, again.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby mysticturner » Sat Jan 21, 2023 5:15 am

I've been getting (and still am) outbound emails being rejected and inbound emails never making it to me. So I've been digging into it. My hypothesis is that there is an issue occurring with DNS lookups on the SG server. The long explanation as to how I got here is below the questions.
Questions:
Has anyone checked if the SG server is correctly resolving DNS names?
Do we need to flush the DNS cache or perhaps recycle it?
Is there a hosts file that is causing problems?

The path to get to the hypothesis.
The key for me was when I sent an email from a gmail account to an SG email address. In the email message/delivery-status section (below) Google presented the 550 error in a slightly different way. The new bit I saw is shown in purple. Looking at the address in the 550 diagnostic message, it points back to google, specifically a DNS lookup shows mail-oa1-f53.google.com. Looking at other emails sent from other email domains, the address reflects the source MTA.

Reporting-MTA: dns; googlemail.com
Arrival-Date: Fri, 20 Jan 2023 19:36:41 -0800 (PST)
X-Original-Message-ID: <CALU=J0P=eNthxZZw7o_+VFZFg2ZxDxTTH9bgrCZqGAUoLphuAw@mail.gmail.com>
Final-Recipient: rfc822; yyyyyyyy.xxxxxxxxxx@ordinaryamerican.net
Action: failed
Status: 5.0.0
Remote-MTA: dns; gourmet7.spamgourmet.com. (216.75.62.102, the server for the
domain ordinaryamerican.net.)

Diagnostic-Code: smtp; 550-X-Host-Lookup-Failed: Reverse DNS lookup does not match for 209.85.160.53
550 (deferred)
Last-Attempt-Date: Fri, 20 Jan 2023 19:37:02 -0800 (PST)

The Remote-MTA, which is gourmet7, is the server generating the 550 error. The Reporting-MTA is only the server that received the error message from gourmet7. Looking at the address in the 550 diagnostic message, it points back to google, specifically a DNS lookup shows mail-oa1-f53.google.com. Looking at other emails sent from other email domains, the address reflects the source MTA. What I think is occurring is that when the email MTA that services email inbound to and outbound from SG, his requests to the DNS resolution server is getting back invalid data.

In more detail, using the example of an email coming in from gmail:
1) gmail server contacts the email server at SG.
2) the SG email server wants to verify who is sending it, so it does a reverse lookup by doing a DNS resolution.
3) the DNS resolver sends back either an error or an address that is not 209.85.160.53 (mail-oa1-f53.google.com).
I don't think the actual SG software is actually getting the opportunity to process the email.
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Location: Dallas, TX

Re: 0sg.net bouncing for bad reverse lookups?

Postby mysticturner » Sat Jan 21, 2023 5:59 pm

I opened a chat with namecheap and talked to them about the issue. At this point, I'm thinking there might be some sort of security problem or DNS configuration problem that is causing all our MAIL FROM reverse lookups to fail. They are wanting me to open up an official ticket. I have no idea what our userid/password(s) with namecheap are. I assume that probably only Josiah has that info.

Has anyone tried updating the DNS server list to point to someplace like google? It's configured in the /etc/resolv.conf but there's a tool to update that file, can't remember it right now.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby skyrock » Sat Jan 21, 2023 8:14 pm

Does anyone operate his own mail server? If so, could you run the following command on Linux and post the result (without posting your IP)?

Code: Select all
dig @dns1.registrar-servers.com  +noall +answer -x XOUR.SERVERS.IP.HERE


For my server the Namecheap DNS returns no result while all other DNS (like Google) do.
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Re: 0sg.net bouncing for bad reverse lookups?

Postby akinet » Sun Jan 22, 2023 7:35 pm

In my case, I have tested spamgourmet accounts sending emails from Yahoo, GMX, Zoho and Gmail. And, right now, only Gmail is rejecting emails with message:
Code: Select all
550 X-Host-Lookup-Failed: Reverse DNS lookup does not match for 209.85.214.182 (deferred)

Does anyone know how to force Gmail to renew DNS server information?
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