Hi everyone,

a user of company told me that a sender couldn't contact him via mail and receive some error with 4.3.2 in result.

Our company use a symantec brightmail that first get messages and redirect to exchange. Brightmail logged that message and correctly delivered it to exchange server without errors or warnings.

However, I searched in ECP -> mail flow -> delivery reports and there is NO trace of that mail message.

I tried testconnectivity.microsoft.com -> Inbound SMTP Email and got this error:

Warning: Analyzing SMTP Capabilities for server smtp01.mydomain:25
The test passed with some warnings encountered. Please expand the additional details.
Unabled to determine SMTP capabilities. Reason: Unexpected SMTP server response. Expected: 220, actual: 450, whole response: 450 4.3.2 try again later
Elapsed Time: 303 ms.

Error: Delivery of the test email message failed.
     
    Additional Details
     
The server returned status code 450 - Mailbox unavailable. The server response was: 4.3.2 try again later
Exception details:
Message: Mailbox unavailable. The server response was: 4.3.2 try again later
Type: System.Net.Mail.SmtpException
Stack trace:
at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at Microsoft.Exchange.Tools.ExRca.Tests.SmtpMessageTest.PerformTestReally()
Elapsed Time: 279 ms.

I tried for many users and find out that many of the tests fail. However most of mails work (inbound and outbound).

The very very dangerous point is that some mail are not even tracked in exchange for some messages.

Any help please ?

Hello

Enable verbose logging on smtp receive connector /if not have/ and search in log to specified data and sender. or Get-MessageTrackingLog search email.

Hi 

For the affected user try to drop an email through telnet from externally and see the results

Make sure that the SMTP filtering in the symantec bright mail is not causing this issue 

The better way of troubleshooting can be below as per my suggestion

1) Disable all the transport agents on the exchange servers and try sending email to the affected user from external account and see the results.

If this test passes then there is some problem with the exchange agents.

If the issue is same even after disabling exchange transport agents then im sure that the problem is with the Symantec Bright Mail and you will need to open a ticket with them