Actually, it is a good idea to turn off inbound pipelining anyway.
There is apparently a lot of spamware that will attempt to bypass your local policy settings by ramming an entire SMTP conversation into a single packet and then closing the connection before your MTA has a chance to issue 554.
http://tinyurl.com/6j5h
I don't think this will cause a Domino MTA any serious problems, but it might tie up one of your inbound handlers for a while.