@Override
	public void write(final int b) throws IOException {
		lastBytes[0] = lastBytes[1];
		lastBytes[1] = (byte) b;
		super.write(b);
	}
The last bytes written out by the {@link #write()} function. The first byte
in the array contains the penultimate, the second contains the last byte
written out by the write function. It's initial value is CR LF, so it is
possible to write out empty data.
src/main/java/de/gessnerfl/fakesmtp/smtp/io/DotTerminatedOutputStream.java