Can the program process messages with addresses in the field BCC (hidden copy)?

BCC is not a usual message header. When you write a message and specify an addressee in the BCC field, your mail client tells the SMTP server to send the message to this addressee and then to remove this header.

NPC can process such messages (arriving in the global mailbox) only if this header is present in some other form. You should check headers of similar messages and find headers which contain the correct addressee. After that you can add this header to the option field 'Additional headers to search recipients in' into the properties of the connector.