We have a CRM web application hosted on a server. When a user launches the site, the site provides facility to the customer to send the query into the system using the email. The website provides the filed for the customer to enter customers email ID. The customer email address is used by the system to send the response back.

We are doing a new implementation for SMTP authentication for the emails send into the contact center using a public website. The flow of the system to use the SMTP authentication is:

1. Customer launches the website.
2. Customer chooses to send the his/her query using the email from the website.
3. Website asks for the customers address, so that the query can be  answered back to the provided email address say customer@gmail.com .
4. We have an account configured on the MS-Exchange 2010 say support@system.com
5. So before sending the email the website system performs the SMTP Authentication using the credentials of support@system.com   
6. Now the system creates the email MIME using the email address provided by the customer on the website i.e. say customer@gmail.com.
7. After successful SMTP authentication for the address   support@system.com system starts sending the email.
8. Here we are facing the issue:

While sending the email if the customers address is also configured on the same exchange used by the system i.e. exchange on support@system.com is configured  then website system is able to relay or send the email.

If the customers address is not configured on the same exchange used by the system where support@system.com is configured then the system is not able to send the email it results into the error of: Client does not have permission to send as this sender customer@gmail.com.

In short if the website performs the  SMTP authentication then it requires the FROM address configured on the same exchange used for the smtp authentication in the email MIME from address.

Configuration tries:

1. As suggested on various forums and at Microsoft tech group we tried following things but no success:
   1. Checked the checkbox Authenticated Users  selected Accept any Sender.
   2. Created a new relay and given the IP of the machine hosting the website or trying to send the email
   3. Run the command from the EMC Exchange management console

Add-AdPermission -Identity "Default Receive Connector" -User "NT AUTHORITY\Authenticated Users" -ExtendedRights ms-Exch-SMTP-Accept-Any-Sender.

You can create a new connector to which everything is permitted - eg New-ReceiveConnector -Name "Anonymous Relay" -Usage Custom -PermissionGroups AnonymousUsers -Bindings 10.2.3.4:25 -RemoteIpRanges 192.168.5.77