Question : Exchange 2007 cannot receive external email

Iam using exchange 2007 in windows 2003 x64.
For one week my server can't receive email that sent from external (ex: yahoo, gmail,etc)
No problem when sending or receiving email in LAN.
No problem when sending email to external.
I had activate log in receiver connector, but no log file created.
Anonymous option in receiver connector already checked like before.

When i try sending email from external to internal account, there's delivery report from my exchange postmaster (so there's no problem with firewall and mx)
Reporting-MTA: dns;myhostname.mydomainname.com
Received-From-MTA: dns;mail-gx0-f215.google.com
Arrival-Date: Tue, 5 Jan 2010 13:21:24 +0700

Final-Recipient: rfc822;Administrator@mydomainname.com
Action: failed
Status: 5.0.0

Answer : Exchange 2007 cannot receive external email

There should be no SMTP service with Exchange 2007.

Have you installed the SMTP service as part of IIS?
If so please uninstall it.