[Mailman-Developers] Mailman 3 and LMTP

[Patrick Ben Koetter]

Hi!

* Barry Warsaw <barry at python.org>:
> I'm getting very near ready to release another alpha of Mailman 3, and on the
> prompting of a private message from Robert Niederreiter I took some time to
> fire up a VM and actually try Postfix+LMTP delivery in an experimental
> production system.  I'd like to get some feedback from the Postfix experts in
> the crowd so that we can update the wiki page here:
> 
>     http://wiki.list.org/display/DEV/LMTP+process
> 
> FTR: the VM is running Ubuntu Karmic Koala 9.10 server with Postfix 2.6.5 and
> Mailman 3.0 from the lp:mailman bzr trunk.
> 
> To start with, I mostly followed the instructions in the wiki.  I tried using
> the standard lmtp transport in master.cf, creating /etc/postfix/mailman_lists
> as described in the wiki (not the dedicated list server example, but the
> earlier one on the page).  I actually used:
> 
> # Key                   # Value
> test at xxx.example.com    lmtp:xxx.example.com
> 
> where 'xxx.example.com' is replaced by my VM's host name.

Additionally you probably want to add square brackets around the hostname.

Quoting "man 5 transport":

  ...the [] suppress MX lookups.  This prevents mail routing loops when your
  machine is primary MX host for example.com.

> The first gotcha is that unless you start Mailman as root, you can't bind its
> LMTP server to port 24, which is Postfix's default.  By default Mailman's LMTP
> server listens on localhost:8024, so you either need to append ':8024' on the
> Value above, or set
> 
>     lmtp_tcp_port = 8024
> 
> in Postfix's main.cf.  I ended up doing the latter, but both work.

I think an option in MM3 should make this configurable.


> I set up transport_maps and local_recipient_maps just as outlined in the wiki
> page, fired everything up, and then sent a message to the VM's Postfix while
> tailing the logs.  I kept seeing "Connection refused" messages from Postfix
> and it never hit Mailman's LMTP server.
> 
> This was highly confusing because I could see in the Postfix logs that it was
> finding the right IP address for its own hostname and it was trying the right
> port number.  Mailman's lmtp.log file claimed it was listening on the right IP
> and port, and I could even telnet to it just fine.  So what was Postfix doing?
> 
> It seems that Karmic is playing tricks with /etc/hosts.  I've got DNS set up
> to correctly resolve the VM's hostname, but there was actually an entry in
> /etc/hosts that set xxx.example.com to 127.0.1.1.  I'm not entirely sure which
> process looks at what, when, but clearly this inconsistency was a key part of
> the problem.  The other thing that surprised me was that Postfix was also

On a sidenote: It also confuses a dhcpd server running on a machine that
promotes 127.0.1.1 to be xxx.example.com. I've opened a bug ticket for that
two Ubuntu releases ago, but it seems they only keep carrying it further from
release to release instead of addressing it. At least that's the impression I
get without knowing the real cause.


> consulting /var/spool/postfix/etc/hosts, and I had to change both /etc/hosts

That's because LaMont Jones delivers the Debian/Ubuntu Postfix package
chrooted. If Postfix runs chrooted it uses /var/spool/postfix/etc/hosts
instead of /etc/hosts.

> and that file as well, so that the IP addresses jived with DNS.  This is
> unsatisfactory, but it seemed critical to getting things working.
> 
> The last piece of the puzzle was to not use Postfix's standard lmtp server in

lmtp client... SCNR

> master.cf, but to define a new one like so:
> 
> mailman3 unix - - - - - lmtp -o disable_dns_lookups=yes
> 
> and then change the mailman_lists transport map to
> 
> # Key                   # Value
> test at xxx.example.com    mailman3:xxx.example.com
> 
> After a restart, everything suddenly worked exactly as expected.

suddenly... :)


> Robert was having a different problem, but hopefully he will follow up here
> with his experience and let us know if any of the above helps.  If any Postfix
> experts have words of wisdom to make this better, please let me know.

If MM relies on Postfix defaults and the postmaster changes them in Postfix
the MM part might end up being unusable. 

I recommend to take full control of the settings in the Postfix transport map.
Let MM create its own Postfix style transport map. Set the "Postfix service
name" (in your example its mailman3), put the hostname in square brackets and
set the port.

> I probably need to work on better dropping of privileges for qrunners so that
> you can 'bin/mailman start' as root, and once the LMTP runner binds to port
> 24, it can drop privs to 'mailman'.  I'll put that on the list for something
> to do after the next alpha.

I like that idea.


> I'd also like to try to resurrect William Mead's LMTP branch.  Sadly, it won't
> merge cleanly into trunk any more (not the least of which because it's in the
> wrong bzr format).  If anybody would like to contribute that before I get to
> it, I'd be grateful.
> 
> The good news is that I think Mailman 3 is getting more real every day.  My
> plan over the next few weeks is:
> 
> * release alpha 4
> * get i18n translations working
> * complete the split of the pipermail project
> * hopefully get Patrick and friends going on the web u/i

I will update to the latest branch that should fix the language file problem
we had discovered and then we will work on the REST client/server.

p at rick

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