[Dovecot] LMTP troubles

[Phillip Odam]

Background:

    Dovecot: v 2.0.9
    OS: AWS Linux (derived from CentOS)

At this stage I've avoided upgrading to a newer version of Dovecot as 
version 2.0.9 is what AWS Linux provides and I'd like to be able to run 
a regular AWS Linux installation if I can. As opposed to pulling newer 
versions of dovecot from other repositories or building from source, 
since the odds are this issue is not a bug in dovecot.

I've just tried setting up the LMTP service and eventually uncovered 
that that the greeting the server responds with straight after 
connecting isn't being returned. This must be a configuration mistake on 
my behalf but I just haven't been able to figure it out yet. I haven't 
had LMTP configured for awhile but I'm sure I've had it all in place and 
don't recall any issue like this.

I've followed the detail here http://wiki2.dovecot.org/LMTP, in particular

# add lmtp to protocols, otherwise its listeners are ignored
protocols = imap pop3 lmtp

service lmtp {
   inet_listener lmtp {
     address = 192.168.0.24 127.0.0.1 ::1
     port = 24
   }

   unix_listener lmtp {
     #mode = 0666
   }
}

What's also interesting, using telnet my first attempt to connect 
results in the server closing the connection immediately and then a 
second attempt to connect results in an established connection but no 
response from the server so that then the LMTP client knows it's all 
good to begin issuing commands.

I have no idea about the architecture of dovecot and the LMTP service 
but it's as if dovecot has successfully bound to the port allocated for 
LMTP* but the the LMTP service has either not started or dovecot doesn't 
know which service to pass the connection on to.

* - dovecot has definitely bound to the port (localhost:24) as netstat 
clearly shows this.

I've tried enabling debug logging per the details here 
http://wiki2.dovecot.org/Logging and checked that I'm looking at all the 
logs I need to be using doveadm log find but not seeing any information 
that helps. At the moment I know I'm light on necessary detail for 
anyone to help but I thought I'd try in case anyone has seen this before 
and is able to tell me I've missed X and Y.

I'm planning on setting up a clean environment to sort this issue out 
and if needed will follow up here with more detail and the final solution/s.

Thanks
Phillip