There are times when you need to allow applications
to relay through your Exchange 2007 or 2010 Server. These steps give two options
for allowing this.
Allow all computers which successfully authenticate
to relay, regardless of the list above
Like its predecessor, Exchange 2007 is configured to accept and relay email from hosts
that authenticate by default. Both the "Default" and "Client" receive connectors are
configured this way out of the box. Authenticating is the simplest method to submit
messages, and preferred in many cases.
The Permissions Group that allows authenticated users to submit and relay is the "ExchangeUsers"
group. The permissions that are granted with this permissions group are:
NT AUTHORITY\Authenticated Users {ms-Exch-SMTP-Submit}
NT AUTHORITY\Authenticated Users {ms-Exch-Accept-Headers-Routing}
NT AUTHORITY\Authenticated Users {ms-Exch-Bypass-Anti-Spam}
NT AUTHORITY\Authenticated Users {ms-Exch-SMTP-Accept-Any-Recipient}
The specific ACL that controls relay is the ms-Exch-SMTP-Accept-Any-Recipient.
Only the list below (specify IP address)
This option is for those who cannot authenticate with Exchange. The most common example
of this is an application server that needs to be able to relay messages through Exchange.
First, start with a new custom receive connector. You can think of receive connectors
as protocol listeners. The closest equivalent to Exchange 2003 is an SMTP Virtual
Server. You must create a new one because you will want to scope the remote IP Address(es)
that you will allow.
The next screen you must pay particular attention to is the "Remote Network settings".
This is where you will specify the IP ranges of servers that will be allowed to submit
mail. You definitely want to restrict this range down as much as you can. In this
case, I want my two web servers, 192.168.2.55 & 192.168.2.56 to be allowed to
relay.
The next step is to create the connector, and open the properties. Now you have two
options, which I will present. The first option will probably be the most common.
Option 1: Make your new scoped connector an Externally Secured connector
This option is the most common option, and preferred in most situations where the
application that is submitting will be submitting email to your internal users as
well as relaying to the outside world.
Before you can perform this step, it is required that you enable the Exchange Servers
permission group. Once in the properties, go to the Permissions Groups tab and select
Exchange servers.
Next, continue to the authentication mechanisms page and add the "Externally secured"
mechanism. What this means is that you have complete trust that the previously designated
IP addresses will be trusted by your organization.
Caveat: If you do not perform these two steps in order, the GUI blocks you from continuing.
Do not use this setting lightly. You will be granting several rights including the
ability to send on behalf of users in your organization, the ability to ResolveP2
(that is, make it so that the messages appear to be sent from within the organization
rather than anonymously), bypass anti-spam, and bypass size limits. The default "Externally
Secured" permissions are as follows:
MS Exchange\Externally Secured Servers {ms-Exch-SMTP-Accept-Authoritative-Domain}
MS Exchange\Externally Secured Servers {ms-Exch-Bypass-Anti-Spam}
MS Exchange\Externally Secured Servers {ms-Exch-Bypass-Message-Size-Limit}
MS Exchange\Externally Secured Servers {ms-Exch-SMTP-Accept-Exch50}
MS Exchange\Externally Secured Servers {ms-Exch-Accept-Headers-Routing}
MS Exchange\Externally Secured Servers {ms-Exch-SMTP-Submit}
MS Exchange\Externally Secured Servers {ms-Exch-SMTP-Accept-Any-Recipient}
MS Exchange\Externally Secured Servers {ms-Exch-SMTP-Accept-Authentication-Flag}
MS Exchange\Externally Secured Servers {ms-Exch-SMTP-Accept-Any-Sender}
Basically you are telling Exchange to ignore internal security checks because you
trust these servers. The nice thing about this option is that it is simple and grants
the common rights that most people probably want.
Option 2: Grant the relay permission to Anonymous on your new scoped connector
This option grants the minimum amount of required privileges to the submitting application.
Taking the new scoped connector that you created, you have another option. You can
simply grant the ms-Exch-SMTP-Accept-Any-Recipient permission to the anonymous account.
Do this by first adding the Anonymous Permissions Group to the connector.
This grants the most common permissions to the anonymous account, but it does not
grant the relay permission. This step must be done through the Exchange shell:
Get-ReceiveConnector "CRM Application" | Add-ADPermission
-User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "ms-Exch-SMTP-Accept-Any-Recipient"
In addition to being more difficult to complete, this step does not allow the anonymous
account to bypass anti-spam, or ResolveP2.
Although it is completely different from the Exchange 2003 way of doing things, hopefully
you find the new SMTP permissions model to be sensible.
Source: http://msexchangeteam.com/archive/2006/12/28/432013.aspx
Applies to: Exchange 2007, Exchange 2010, Exchange Server 2007, Exchange Server 2010,
Backup Exec, Symantec Backup Exec, Symantec Backup Exec 12.5
