public void execute(CommandParser commandParser) throws IOException,
Pop3Exception {
if (session.getSessionState() != AUTHORIZATION)
throw new IllegalSessionStateException();
if (session.isTlsStarted())
throw new Pop3Exception(null,
"Command not permitted when TLS active");
session.getThread().sendResponse("+OK Begin TLS negotiation");
SSLSocket sslSocket =
session.getServer().getTlsConfiguration()
.createSSLSocket(session.getThread().getSocket());