logging LMTP activity

[Janis]

Hello,

I've been trying to set up Postfix + Dovecot LMTP setup. Basic idea 
taken from https://wiki2.dovecot.org/HowTo/PostfixDovecotLMTP, but since 
Postfix is on different host inet listener is used instead of unix socket.

Message delivery works. Messages are delivered to correct mailboxes, if 
they exist.

But the problem is with logging on Dovecot side; i can not get any lmtp 
logs at all. I kind of expected that i could get logs about:
1) Postfix has connected and delivering mail to mail at address.com,
2) If mailbox does not exists, would expect to see in logs the reason 
for rejection - mailbox does not exist
3) any other useful info would be nice as well.

How do you get LMTP to log something? My Dovecot version is 2.3.11.3. 
Basic IMAP logging is working. I see when users have connected, etc.

I tried as suggested at 
https://doc.dovecot.org/configuration_manual/protocols/lmtp_server/#logging

If the given logging example block is used in configuration, i get no 
logs in file /var/log/dovecot-lmtp.log. I thought maybe file is not 
created automatically, so i tried to create it myself as well. Does not 
work. chmod 0777 does not either, chown to dovecot:dovecot neither.

In a way i am curious about "executable = lmtp -L" part. What is -L 
flag? Are there any more flags? Where could i learn about them? I have 
read all the docs that come with the buld and mention something of lmtp, 
it's basically wiki, i guess... but i could not find any helpful info.

I found that file lmtp is at /usr/local/libexec/dovecot/lmtp. When i 
execute it with -L flag it works. Other flags don't. The problem is that 
there are no -h or --help flags.


Then i tried raw logging as described here: 
https://doc.dovecot.org/admin_manual/debugging/debugging_rawlog/#debugging-rawlog

As i understand, only 4th possibility is applicable to LMTP, am i right? 
2nd kind of seems maybe somehow could be usable, but i don't see how...

It is not clearly stated in wiki where "lmtp_rawlog_dir" should be 
added, but i add it within "protocol lmtp { .. }" block, similar as 
imap. Does not work for me - no logs while messages arrive.  The catchy 
part in wiki is that for imap special arguments are used "-R rawlog" in 
service imap-login, postlogin.  But i don't see any lmtp-login or such 
service available. So should it work only with "lmtp_rawlog_dir" option?

What could i be doing wrong?

Does anyone have working lmtp configuration with logging available?

Thank you very much! I am sorry that my message is so long, but i tried 
even more to get it working... :)

Any help or idea of how to better debug the situation or search for 
solution is kindly appreciated.