Exchange Server - all of a saden one email is not able to recieve external emails

All of a saden one email is not eble to recieve external emails in exchange server 2007 but it can send, and other emails  are working properly. this has been happening for almost a month now. i am gettting an error below from gmail.

This is an automatically generated Delivery Status Notification.

Delivery to the following recipients failed.

    myemail@domain.com

Final-Recipient: rfc822;myemail@domain.com
Action: failed
Status: 5.1.1
Diagnostic-Code: smtp;550 5.1.1 User unknown

This sounds like a MS exchange error, can you get with your IT folks an have them check it for you.
here is some more information about the error code.
Numeric Code: 5.1.1

Possible Cause:

• The e-mail account does not exist at the organization the message was sent to. This issue may occur if there was a problem when users were moved between sites. For example, if a former Administrative_Group_1 user moves to Administrative_Group_2 and then replies to an old e-mail message, or if the user does not re-create his or her Outlook profile, an old Administrative Group style LegDN address will be used, and an NDR is generated.
• The message was sent to obsolete personal address book entries.
• The categorizer rejected delivery because you configured your SMTP contact with see comment SMTP RFC821 characters.

and here is a link to information about the http://support.microsoft.com/kb/257186 code

Don

hi,

Basically this is not your mistake. The email address you were sending to  was disabling for a number of reason. so please check your gmail groups to solve this.

Regards,

In a single-server Exchange 2007 setup you'll need to allow annonymous connections on your default receive connector.  By default Exchange 2007 servers not running the Edge Transport role will only accept inbound smtp connections from Exchange Users (clients), Exchange Servers (other Exchange 2007 servers) and Exchange Legacy Servers (legacy Exchange 2003 & below servers).  To allow annonymous smtp connections for your server, run the following management shell command:

Set-ReceiveConnector -Identity "Default <ServerName>" -PermissionsGroup "AnonymousUsers"

As for not being able to send external email, have you configured a Send Connector?  This is done through Organizational Configuration->Hub Transport->Send Connectors, or by using the management shell command New-SendConnector.

Hope this helps,

thanks Yadav for this input, but nothing was changed on the exchange server it all happened one morning.

thanks Yadav for this input, but nothing was changed on the exchange server it all happened one morning.

thanks for this input, but nothing was changed on the exchange server it all happened one morning.

Well,

I have to belive you when you say nothing changed, however I would respectfully submit that if it is no longer working. then something did change, somewhere.  perhaps not in the exchange server but that is more likely where it happened based on the error code. 

Are you the Admin on the Server for Exchange?  Have you addressed your error with them if you are not?
Who is your internet provider and have you contacted them to see if something changed with your service.  I have several POP3 accounts from the web that I have outlook 'go and get' I have changed my SMTP and POP information accidentally while setting up a second one and lost the inbound /outbound ability to send / receive mail. 

I am sure by now you have tried to send yourself email from different machines within your workgroup or internally.

Perhaps you can try to send mail to a different user in your exchange from an external source and troubleshoot whether or not it is that one named recipient not getting mail or all email address on the server. 

Let us know how this works and if you are still having issues.  perhaps we can do some more research with some more information. 

Don