Every day is a school day. I have been looking for this for ages. Basically I want to populate the Allow list on an SMTP virtual server programatically .. and this KB tells you how: http://support.microsoft.com/kb/810913
Microsoft Exchange 2000 provides connection and relay control for its Simple Mail Transfer Protocol (SMTP) virtual servers. An administrator can use these controls to limit the computers that can connect to a virtual server or that can relay e-mail to outside the Exchange 2000 organization. You can view these controls by using Exchange System Manager.
An Exchange 2000 post-Service Pack 3 (SP3) hotfix introduces a programmatic interface to the SMTP Virtual Server Connection Control settings and the Relay Control settings. The Exchange IP Security Component Object Model (COM) interface (ExIPSec) provides an additional way to access these control settings.
ExIPSec allows an administrator to programmatically view and modify the connection settings and relay control settings on an Exchange 2000 server. In certain circumstances, an administrator can modify these settings in bulk on servers throughout the organization to lower the total cost of ownership of Exchange 2000.
Essentially it’s ExIPSec.dll. Now the above KB has it for Exchange 2000 but not for Exchange 2003.
This is the update for Exchange 2003: Microsoft Exchange Server SMTP Internet Protocol Restriction and Accept/Deny List Configuration
Use the SMTP Internet Protocol Restriction and Accept/Deny List Configuration to programmatically set or view Internet Protocol (IP) restrictions on an SMTP virtual server and to add or remove IP addresses from your global accept or deny lists. Microsoft Exchange 2003 provides connection and relay control for its Simple Mail Transfer Protocol (SMTP) virtual servers. Additionally, Exchange 2003 provides connection filtering that allows you to configure IP addresses from which you want to accept connections or from which you want to always deny connections. These settings are configured in global accept and deny lists in Connection Filtering. An administrator can use these controls to limit the computers that can connect to a virtual server or that can relay e-mail to outside the Exchange organization.
Note This tool can be used against Exchange 2000 servers but the global accept and deny list configuration is only applicable to Exchange 2003 servers. If Active Directory has been updated with the Exchange 2003 schema then the tool can be used to configure entries on the global accept and deny lists, but this configuration is only available on Exchange 2003 servers.