Ilja, I still can't seem to get my Postfix talking to the LMTP daemon :-( Something that I had never specifically tested, though, is what happens when you connect to the same process that you'd previously connected to and closed? Looking at the output and reading over the code again led me to believe that some data might have been hanging around after the end of a connection only to haunt the next connection. This should now be cleaned up.
I have not tried delivering a message, then waiting for a timeout, then trying again. My hunch is that a call to lmtp_reset() needs to be made from the timeout alarm signal handler... I won't be up tonight, so I hope that this might be the clue you need to fix this bug and clear the way for 2.0rc3. Best of luck! Aaron
