Я удостоверился бы, что сделал следующее:
Assuming you've created your internal receive connector properly (locked down to Nagios IP) you need to run this command:
Get-ReceiveConnector RelayConnector | Add-ADPermission -User “NT AUTHORITY\ANONYMOUS LOGON” -ExtendedRights “ms-Exch-SMTP-Accept-Any-Recipient”
This will enable the specific permission that enables an open relay. This is disabled by default on all connectors created.