Indeed, at £1k (€1136, $1403) one might as well run an internal application. At a very basic level, it can be achieved with three lines of bash:

    while echo -en "HTTP/1.1 200 OK\r\n..." | nc -l $IP $PORT; do
        cat $MESSAGE | sendmail -i -t
    done

More complex configurations could still be worked out in <50 lines of Python.