Question : Exchange Server 2003 SMTP error

This seems to be a common question, but I still seem to be having issues.

Your message did not reach some or all of the intended recipients.

      Subject:     Origianl Subject
      Sent:     Date Time

The following recipient(s) could not be reached:

      'Recipient Mail Address' on Date Time
            You do not have permission to send to this recipient.  For assistance, contact your system administrator.
            >

I have a SBS2003 Server with Exchange 2003 running where all inhouse email and most outside email goes through without incident.  I am however running into an issue where the above error is coming back to us on, at this time, only one address.  

I have checked for the possibility of being on a RBL list and I'm not listed.  I have checked the relay for authenticated machines and it is active.  I have also looked at responses about the Reverse PTR and I have my internal IP and external IP listed.

Any further thoughts would be greatly appreciated.

Thanks

Answer : Exchange Server 2003 SMTP error

Your problem is most likely due to fixup protocol being turned on at the PIX:

>fixup protocol dns maximum-length 512

http://support.microsoft.com/?id=828263

Check your PIX IOS first.  You need to have at least 6.3(2).
To check this, logon to PIX and then type (show version)

To change fixup protocol issue:

Login to the PIX
Go to enable mode (en)
Go to terminal mode (conf t)
Type:  no fixup protocol dns
Type: write mem

You're done.