ActiveXperts Knowledge Base Article 3500015
On the webserver, the IUSR_<computername> credentials are used for all SMS operations. The IUSR_<computername> is only member of the Guests group by default; it doesn't have sufficient permissions to query the Windows Telephony Devices. By making the IUSR_<computername> account member of the Local Administrators group, you will be able to see all Windows Telephony Devices.
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