OnTOP is a TIdPOP3ServerTOPCommandEvent property that represents the event handler signalled when a threaded client connection performs the POP3 TOP command verb. 

OnTOP allows the server to implement the optional POP3 command, and performs processing required to extract message headers and the specified number of body lines for the indicated message number. 

OnTOP is responsible for generating the initial Positive POP3 response, followed by message headers, a blank line, the number of body lines requested, and the terminating '.' character. If the number of lines requested by the POP3 client is greater than the number of lines in the body, then the POP3 server sends the entire message. 

OnTOP is triggered by the TIdCommand event handler that implements support for the POP3 TOP command for the client context. OnTOP is not triggered for a client connection where TIdPOP3ServerThread.State contains a value other than Trans, or the event handler has not been assigned. 

OnTOP is responsible for writing the positive POP3 response to the client connection. Negative POP3 responses are written by the TOP command handler when TIdPOP3ServerThread.State contains a value other than Trans, the OnTOP event handler has not been assigned, or when an invalid number of arguments are available from the TOP command issues to the server. 

It is recommended to implement support for the TOP command. Messages marked for deletion should not be included in the TOP listing.

TIdPOP3ServerTOPCommandEvent TIdPOP3ServerThread.State TIdCommandHandlers TIdCommandHandler TIdCommand