Re: [mailop] SMTP disconnect… (Was: Hosteurope contact?)

[Hans-Martin Mosner via mailop]

Am 07.05.23 um 00:12 schrieb Thomas Walter via mailop:

Turns out

mx-out-02:~$ nc mx0.webpack.hosteurope.de 25
220 mx0.webpack.hosteurope.de ESMTP (mi005.mc1.hosteurope.de) (even more power) 
Sun, 07 May 2023 00:03:13 +0200
ehlo mx-out-02.fh-muenster.de
550-REJECT: 212.201.120.206 is in csi.cloudmark.com :
550-Listed as Poor Reputation Sender. Cloudmark Sender Intelligence Reputation
550 Remediation Portal https://csi.cloudmark.com/en/reset (ID:550:3:0)
mx-out-02:~$

All this trying to figure out what's going wrong, contacting support, etc. could've been avoided if they followed the 
RFC?


https://www.rfc-editor.org/rfc/rfc5321#section-4.1.1.10

4.1.1.10.  QUIT (QUIT)

   This command specifies that the receiver MUST send a "221 OK" reply,
   and then close the transmission channel.

   The receiver MUST NOT intentionally close the transmission channel
   until it receives and replies to a QUIT command (even if there was an
   error).

Or is there a new version to the standards that allows this? 


It's probably not sanctioned by the standards, but considering the aggressive push of spam mails into our systems I can 
understand when mailops reduce communication with a perceived bad sender to a minimum. However, a properly coded 
mailserver should adhere to the standards even if its operators choose to turn away SMTP clients early.


OTOH, your mail server acting as an SMTP client should handle the 550 code and at least log it, even if the other side 
behaves out of spec. Such information can be useful.


Cheers,
Hans-Martin

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[mailop] SMTP disconnect… (Was: Hosteurope contact?)

[Thomas Walter via mailop]

Hello,

according to replies from Hosteurope it turns out our server with 
212.201.120.206 is listed on csi.cloudmark.com.


I can't find an RBL check to confirm that. The following two say, it is not:

https://tinycp.com/page/show/rbl-check
https://whois.smartweb.cz/en/blacklist/check/212.201.120.206/

And it is not listed anywhere else either

https://mxtoolbox.com/SuperTool.aspx?action=blacklist%3a212.201.120.206=toolpage

I just tried to have it removed anyway, since it seems to be the only 
way to fix this.


Either way, I was irritated, why we don't get a proper 5xx status code 
in our logs, but just


May  6 23:53:54 mx-out-02 postfix/smtp[14561]:
36119E0288: to=, relay=mx0.webpack.hosteurope.de[80.237.138.5]:25,
delay=306795, delays=306794/0.17/0.18/0, dsn=4.4.2,
status=deferred (lost connection with
mx0.webpack.hosteurope.de[80.237.138.5] while performing the HELO
handshake)

Turns out

mx-out-02:~$ nc mx0.webpack.hosteurope.de 25
220 mx0.webpack.hosteurope.de ESMTP (mi005.mc1.hosteurope.de) (even more 
power) Sun, 07 May 2023 00:03:13 +0200

ehlo mx-out-02.fh-muenster.de
550-REJECT: 212.201.120.206 is in csi.cloudmark.com :
550-Listed as Poor Reputation Sender. Cloudmark Sender Intelligence 
Reputation

550 Remediation Portal https://csi.cloudmark.com/en/reset (ID:550:3:0)
mx-out-02:~$

All this trying to figure out what's going wrong, contacting support, 
etc. could've been avoided if they followed the RFC?


https://www.rfc-editor.org/rfc/rfc5321#section-4.1.1.10

4.1.1.10.  QUIT (QUIT)

   This command specifies that the receiver MUST send a "221 OK" reply,
   and then close the transmission channel.

   The receiver MUST NOT intentionally close the transmission channel
   until it receives and replies to a QUIT command (even if there was an
   error).

Or is there a new version to the standards that allows this?

Regards
Thomas Walter

--
Thomas Walter
Datenverarbeitungszentrale

FH Münster
- University of Applied Sciences -
Corrensstr. 25, Raum B 112
48149 Münster

Tel: +49 251 83 64 908
Fax: +49 251 83 64 910
www.fh-muenster.de/dvz/


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