User cannot receive mail from single client

I have a user that cannot receive email from one of his clients.  The sender does not receive an NDR report but the Exchange logs do not show this message arriving either.   I checked the spam filter on the firewall and the junk filters but come up with nothing.  What am I overlooking? The sender sent the following report showing connectivity to our mail server.

Testing inbound SMTP mail flow for domain 'dave@xxxxx.com'.

Inbound SMTP mail flow was verified successfully.



Additional Details


Elapsed Time: 37648 ms.



Test Steps





Attempting to retrieve DNS MX records for domain 'xxxxx.com'.

One or more MX records were successfully retrieved from DNS.



Additional Details


MX Records Host mail.xxxxx.com, Preference 10

Elapsed Time: 176 ms.




Testing Mail Exchanger mail.xxxxx.com.

This Mail Exchanger was tested successfully.



Additional Details


Elapsed Time: 37471 ms.



Test Steps





Attempting to resolve the host name mail.xxxxx.com in DNS.

The host name resolved successfully.



Additional Details


IP addresses returned: 50.194.64.132

Elapsed Time: 333 ms.




Testing TCP port 25 on host mail.xxxxx.com to ensure it's listening and open.

The port was opened successfully.



Additional Details


Banner received: 220 xxxxx-xxxxx.colo.sonicwall.com ESMTP SonicWALL (7.4.4.8313)

Elapsed Time: 505 ms.




Analyzing SMTP Capabilities for server mail.xxxxx.com:25

The test passed with some warnings encountered. Please expand the additional details.



Additional Details


Unabled to determine SMTP capabilities. Reason: Authentication failed to the SMTP server.

Elapsed Time: 758 ms.




Attempting to send a test email message to dave.terry@xxxxx.com using MX mail.xxxxx.com.

The test email message was delivered successfully.



Additional Details


Elapsed Time: 35366 ms.




Testing the MX mail.xxxxx.com for open relay by trying to relay to user Admin@TestExchangeConnectivity.com.

The Open Relay test passed. This MX isn't an open relay.



Additional Details


The open relay test message delivery failed, which is a good thing. The exception detail: Exception details: Message: Mailbox unavailable. The server response was: 5.7.1 Unable to relay for <Admin@TestExchangeConnectivity.com> Type: System.Net.Mail.SmtpFailedRecipientException Stack trace: at System.Net.Mail.SmtpTransport.SendMail(MailAddress sender, MailAddressCollection recipients, String deliveryNotify, Boolean allowUnicode, SmtpFailedRecipientException& exception) at System.Net.Mail.SmtpClient.Send(MailMessage message) at Microsoft.Exchange.Tools.ExRca.Tests.SmtpOpenRelayTest.PerformTestReally()
NytroZAsked:
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jboddyCommented:
Is it just one person from the client who cannot email, or everyone at the client company?

Does the client use a hosted email system?
If yes, are the hosting company filtering a bit aggressively for "spam"?

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Blue Street TechLast KnightCommented:
Hi torszula,

One user! Have you tried running Message Tracking?

What is the Exchange version? Hosted or OnPrem?
What are you using for Spam filtering?
How is the SonicWALL involved? It looks like it being run from a CoLo.

Let me know so we can solve this for you!
EEhotlineCommented:
Check if the client has added that email address to Block list in his/her Outlook. I have one user did that.
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Md. MojahidExchange server admin Commented:
You have to add that client domain or id on white list. and also check your security setting.
michaelalphiCommented:
First, Please check if any third party external spam Filter are running in system ?
Use mxtoolbox and verify the email address if they are blacklisted.
Else, if you are using any third party white-listing for your recipient addresses then you will have to add their email address manually.
NytroZAuthor Commented:
This is only one user that is having this problem.  we are on an Exchange 2010 server that is hosted on site.  There is a spam filter on the Sonic Wall firewall but the message is not being blocked by it.  the user does not have the address in the blocked list.
NytroZAuthor Commented:
I have checked the message tracking logs but I can't find any messages from the sender.  Since the sender is not getting an NDR and the message is not getting to our mail server then it seems likely that it must be accepted somewhere else, no?  I have once again checked the Sonic Wall Junk Box but the messages are not in there.
NytroZAuthor Commented:
I was able to identify the message in our spam filter.  I don't know why it is detecting it as definite spam yet, but the setting was to delete definite spam.  I changed it to move to junk until I can identify why it is "definite".
jboddyCommented:
We have an external filtering company and have had several problems recently with spam filtering, that is what made me think of it.
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