CheckUser is a TIdPOP3ServerLogin event handler property that represents the event handler triggered to implement identifying and authenticating a client connection after the POP2 PASS command. 

CheckUser is called from the command event handler that implements the TIdCommand for PASS for the threaded client. 

Assign a procedure to the event handler to allow responding to the TIdPOP3ServerLogin event. The procedure is responsible for setting the session state in the TIdPOP3ServerThread.State instance depending on success or failure of the process. The procedure does not have to write positive or negative POP3 responses to the client connection.

TIdPOP3ServerLogin TIdPOP3ServerThread.State TIdCommandHandlers TIdCommandHandler TIdCommand