Exchange not receiving external mail

I am having trouble with our Exchange server at the moment and cannot work out what is wrong. Basically I can receive internal mail on the domain between exchange users but nothing from an external address comes through at all.

I have even tried from my own external account but it doesn't come through on the exchange server. The e-mail doesn't get returned as undelivered and there is no error when doing a manual SMTP to the exchange using an external SMTP server.

Does anyone know what could be wrong?

SBS2003 SP2

You said while using external account e-mail doesn't get returned as undelivered, should I assume it as it worked for you? Also is your MS Exchange configured to accept mail for that domain? Until you reply, just try running few test from mxtoolbox.com and see if your server is all ok.

Or just follow the steps provided in this KB describing “XFOR: Telnet to Port 25 to Test SMTP Communication” http://support.microsoft.com/kb/153119. let me know the results.

Other people can receive external e-mails no problem. Even this individual user can receive e-mails on a different e-mail address but for some reason this one e-mail address is not receiving them.
I cannot give out the e-mail address as it is one of my clients.

Hello Kaotix, just try out these steps and see what happens:

• Start Exchange System Manager.
• Expand Servers, right-click Your_ Server_Name, and then click Properties.
• Click the Diagnostics Logging tab, and then click MSExchangeTransport under Services.
• Under Categories, click the category that you want to log.
• Under Logging Level, click the appropriate logging level for the issue that you are investigating:
  
  1. None
  2. Minimum
  3. Medium
  4. Maximum
• Repeat steps 4 and 5 for each category that you want to log.

Hello, I am having a similar problem as a server that was configured and working 3 days ago is not getting any external email. It was working fine Friday night and now if try to send from Exchange server, the messages just sit in the queue and are not able to be delivered. I have not changed anything and as far as I know, nothing else has changed anywhere. Is there somewhere in Exchange 2007 that I can control the connections like I did in Exchange 2003? I cannot find what the issue is and have run out of places to look.

Please help.

Thank you in advance,

JETalley

Also, if this helps, When I run a telnet test, everything is Ok until to try to email my self from the problem server and I get, Unable to relay. Where is that being controlled at?

Again,

Thanks in advance.

JETalley

Here is the Telnet test I did.

220 mail.domain.com Microsoft ESMTP MAIL Service ready at Mon, 11 Jul 2011 13:
25:10 -0400
ehlo
250-mail.domain.com Hello [x.x.x.x External IP]
250-SIZE 10485760
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-STARTTLS
250-AUTH
250-8BITMIME
250-BINARYMIME
250 CHUNKING
mail from:administrator@domain.com
250 2.1.0 Sender OK
rcpt to:email@externaldomain.com
550 5.7.1 Unable to relay

JETalley