Mail is collected from the POP3 server, but is not delivered to receivers.

NPC receives mail from the external POP3 server then sends it through the internal SMTP server. If during sending there are any errors, the message is moved to the BADMAIL folder. To learn what error has occurred, look at the log of the program NPC-*.log.
Usually, you will see an error of the type: “550 5.7.1 Unable to relay for …”

Solution:

a. Press Start, open Programs \Microsoft Exchange and start System Manager.

b. In Exchange System Manager, open the following object: Servers\Your_Exchange_Server_Name\Protocols\SMTP

c. Right-click the virtual SMTP server chosen in settings of NPC and choose Properties.

d. Go to the Access tab, and then press Relay.

e. By default, the open relay is closed, and “The Only the list below is chosen.

f. Press Add. In the Computer dialog, enter the IP address (or the addresses of all network adapters, one at a time) of the server on which NPC is installed. Press OK.

Another common error is 454 5.7.3 Client does not have permission to Send As this sender …

NPC uses System rights for starting, since it starts as a service before any user login can occur on the server. Therefore, it can use only Anonymous access to the SMTP server.

If for some reason, you cannot allow anonymous access to your SMTP server, you can create another virtual SMTP server, which does allow anonymous access, and limit access to this (virtual) server to the IP server addresses on which NPC is installed. Then choose this new SMTP server in the connector properties. Using this adjustment, NPC and other services of server can use the data of the connector, and users and other computers can use the other SMTP server with authorization.