protected void sendHeloOrEhlo() throws IOException {
		extensions.clear();
		final Response resp = this.sendReceive("EHLO " + heloHost);
		if (resp.isSuccess()) {
			parseEhloResponse(resp);
		} else if (resp.getCode() == 500 || resp.getCode() == 502) {
			// server does not support EHLO, try HELO
			this.sendAndCheck("HELO " + heloHost);
		} else {
			// some serious error
			throw new SMTPException(resp);
		}
	}
Sends the EHLO command, or HELO if EHLO is not supported, and saves the list
of SMTP extensions which are supported by the server.
src/test/java/de/gessnerfl/fakesmtp/smtp/client/SmartClient.java