OnLIST is a TIdPOP3ServerMessageNumberEvent property that represents the event handler signalled when a threaded client connection performs the POP3 LIST command verb. 

OnLIST allows the server to implement generation of a listing containing information about one or more messages in a server mailstore. 

In order to simplify parsing POP3 listings, all POP3 servers are required to use a common format for listings. A scan listing consists of the message-number of the message, followed by a single space and the exact size of the message in octets. Additional information may follow the the message size in the scan listing, and is dependent on the server implementation. It is not, however, encouraged. Each line in the listing must end with a CRLF pair. 

Messages marked for deleteion are not included in a listing. 

OnLIST is triggered by the command event handler that implements the POP3 LIST command for the client context for the connection. 

Assign a procedure to the event handler to allow responding to the event notification. The OnLIST event handler is not triggered if the TIdPOP3ServerThread.State property contains a value other than Trans. 

The event handler is responsible for writing the content for the listing and other positive POP3 responses; Negative POP3 responses are written by the command event handler that triggers OnLIST when TIdPOP3ServerThread.State does not contain the value Trans on entry, or the event handler is unassigned.

TIdPOP3ServerMessageNumberEvent TIdPOP3ServerThread.State TIdCommandHandlers TIdCommandHandler TIdCommand