-/* Before sending an SMTP response in a TCP/IP session, we check to see if
-there is unconsumed input (which there shouldn't be) or if the connection has
-gone away. This can be done because the end of a message is always a
-synchronization point. If the connection is still present, but there is no
-pending input, the result of a select() call will be zero. If, however, the
-connection has gone away, or if there is pending input, the result of select()
-will be non-zero. The two cases can be distinguished by trying to read the next
-input character. Of course, since TCP/IP is asynchronous, there is always a
-chance that the connection will vanish between the time of this test and the
-sending of the response, but the chance of this happening should be small.
+/* Before sending an SMTP response in a TCP/IP session, we check to see if the
+connection has gone away. This can only be done if there is no unconsumed input
+waiting in the local input buffer. We can test for this by calling
+receive_smtp_buffered(). RFC 2920 (pipelining) explicitly allows for additional
+input to be sent following the final dot, so the presence of following input is
+not an error.