email communication problem between 3 domain names

Hello,

One of our customer is facing problems when sending emails to some domain names. The situation is described below:

Assume we have three domain names x.com; y.com and z.com

x.com is hosted at Google. Y and Z are hosted in the US and can be accessed via CPanel. When user alpha@x.com send an email to gamma@z.com the below report is returned:

This is an automatically generated Delivery Status Notification

Delivery to the following recipient failed permanently:

   gamma@Z.com

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550-Verification failed for <alpha@X.com>
550-No Such User Here
550 Sender verify failed (state 14).

  ----- Original message -----

MIME-Version: 1.0
Received: by 10.142.230.9 with SMTP id c9mr1720467wfh.254.1238338409990; Sun,
       29 Mar 2009 07:53:29 -0700 (PDT)
Date: Sun, 29 Mar 2009 17:53:29 +0300
Message-ID: <ce76d9610903290753qb7419a5p61a5b5b3784f7478@mail.gmail.com>
Subject: Test1
From: Test ttc <alpha@X.com>
To: gamma@Z.com
Content-Type: multipart/alternative; boundary=000e0cd17d6a0a09e9046643216d

--000e0cd17d6a0a09e9046643216d
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

Test1

--000e0cd17d6a0a09e9046643216d
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit


  ----- Message truncated -----

The below error is returned when gamma@Z.com send an email to alpha@X.com:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  alpha@X.com
    No Such User Here

------ This is a copy of the message, including all the headers. ------

Return-path: <gamma@Z.com>
Received: from localhost ([127.0.0.1]:37982 helo=Z.com)
        by cayenne.websitewelcome.com with esmtpa (Exim 4.69)
        (envelope-from <gamma@Z.com>)
        id 1LnwLM-0001OK-4b; Sun, 29 Mar 2009 09:50:36 -0500
Received: from 85.112.66.203 ([85.112.66.203])
        (SquirrelMail authenticated user gamma@Z.com)
        by Z.com with HTTP;
        Sun, 29 Mar 2009 09:50:36 -0500 (CDT)
Message-ID: <64898.85.112.66.203.1238338236.squirrel@Z.com>
Date: Sun, 29 Mar 2009 09:50:36 -0500 (CDT)
Subject: Test1
From: gamma@Z.com
To: alpha@X.com
Cc: test@T.com
User-Agent: SquirrelMail/1.4.13
MIME-Version: 1.0
Content-Type: text/plain;charset=iso-8859-1
Content-Transfer-Encoding: 8bit
X-Priority: 3 (Normal)
Importance: Normal

Note also that all users in X.com, Y.com and Z.com can send emails normally to any other domain names like hotmail, yahoo or any other mail hosted at Google. The problem is only between those 3 domain names.

Appreciate your prompt feedback!

Grayhat7Asked:
Who is Participating?
 
Grayhat7Connect With a Mentor Author Commented:
For some reason, the emails are flowing normally again. Case closed!
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FearNoMoreCommented:
Are reverse PTR's configured in DNS for these 3 domains and pointing correctly?
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Grayhat7Author Commented:
How do I check exactly?
0
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FearNoMoreCommented:
Also make sure that connecting ip of x.com is not being blocked by z.com
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FearNoMoreCommented:
Well you need to check in DNS for these 3 domains wheher they have the PTR records configured
To be able to do that....you would need to have access to the DNS servers
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FearNoMoreCommented:
Do you know how to use telnet?
From x.com....use telnet z.com 25
and check the banners and let me know what you see there
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Grayhat7Author Commented:
x.com is hosted on Google's Servers. I have configured the my outlook to retrieve my emails. I access my account on the web using http://mail.x.com. I know how to use telnet, do u want me to telnet the mail.x.com address?

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FearNoMoreCommented:
telnet to x.com port 25
and drop an email to z.com
Check what telnet says
These kinds of issues that you are facing can be due to:
1.Reverse PTR's not configured
2.Connecting IP being blocked by recipeint domain
3.Recipient Domain has blacklisted Sender domain using spamhaus or other XBL or RBL's
 
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tymesCommented:
So stupid domain Z uses callback verification to verify Google hosted domain X exists... (REAL BAD IDEA).... so when X tries to send to Z, at the exact same time Z calls back to X and asks will you accept this message... X is too slow or too stupid and says not right now (which is perfectly acceptable) so Z says ok you don't want my message I don't want yours.

No message is blah..

Worst comes when both X and Z use the same call back verification.. imagine A.com sending a message to B.com... B.com sees the message from A.com and tries to send a message A.com but AGAIN A.com sees message from B.com and tries to send message back to B.com to verify that message.   I'll accept your message if you accept my message ad infinitum.   Nobody will ever get any messages.


Google is sometimes slow enough that it will say no.   Any server (aka Z.com) that has this stupid test is STUPID and you need to MOVE or turn it off (MOVE is better).


This is why I can quote your:

550 550-Verification failed for <alpha@X.com>
550-No Such User Here
550 Sender verify failed (state 14).

They failed not because they don't exist, but because #1, they were too slow (not bad) or #2 they tried to verify the verifiers (my description of example #2).

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tymesCommented:
There are things like greylisting (google it) or again as I said just slow servers or stupid servers that will break smtp....   greylisting is commonly used and better than call back verification (which doesn't break SMTP rules where as call back verification DOES break SMTP rules).

You're problem is "call back verification" done by some of those stupid cpanel domains which is bad in more than in the ways than I've explaind here since it MAGNIFIES the amount of smtp traffic and it can be used for attacks or it can get you blacklisted.... imagine lots of bogus messages that you try to call back and try to verify against spam traps or honey pots or millions of attacks against valid hosts... just STUPID.  You don't want to get a message that has you waste your time with knock knock jokes or "do you have price edward in a can?"   "is your refrigerator running?"   Well, if you try to answer that question 5000 times and say "yes my refrigrator is running" it doesn't matter if you hear them say go catch it or go run after it then....   answering the question is bad enough.


Pay some money and get some better service.  It is their fault you are wasting your time.





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Grayhat7Author Commented:
How do u explain the fact that Z.com can send emails to another domain C.com hosted at Google's servers also. So why C.com accept those emails and X.com refuses to do it?

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Grayhat7Author Commented:
Hello Experts, any updates on the above?
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