Re: [Mailman-Developers] Mailman 3 and LMTP

[Barry Warsaw]

On Nov 29, 2009, at 3:22 AM, Patrick Ben Koetter wrote:

Hi!

* Barry Warsaw <ba...@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


Mailman 3.0 from the lp:mailman bzr trunk.


earlier one on the page).  I actually used:

# Key                   # Value
t...@xxx.example.com    lmtp:xxx.example.com

where 'xxx.example.com' is replaced by my VM's host name.

FTR: the VM is running Ubuntu Karmic Koala 9.10 server with Postfix 2.6.5 and 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

Quoting "man 5 transport":


 machine is primary MX host for example.com.

Additionally you probably want to add square brackets around the hostname. ...the [] suppress MX lookups. This prevents mail routing loops when your

This could have been Robert's problem. I'd forgotten that we actually do create the transport map automatically, if you set the configuration to use Postfix's LMTP delivery (this is the default). In that case, we generate a file called data/postfix_lmtp (and use postmap to create the .db file) which should be usable directly as the transport_map. I've changed it to include the brackets around the host name. This actually greatly simplifies things, since all you need to do is set transport_maps and local_recipients and you're done.

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.

It does. Also putting the port in the Mailman generated transport_map means the right thing will always happen (modulo the permission dropping part which won't make it into 3.0a4).

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

get without knowing the real cause.

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

What's the bug number?

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

instead of /etc/hosts.

chrooted. If Postfix runs chrooted it uses /var/spool/postfix/etc/ hosts

Ah, the pieces click together.  Thanks!

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

Erp. ;)

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
t...@xxx.example.com    mailman3:xxx.example.com

After a restart, everything suddenly worked exactly as expected.

suddenly... :)

Yeah.  Doesn't everybody call 6 hours on a Saturday "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.

the MM part might end up being unusable.


set the port.

If MM relies on Postfix defaults and the postmaster changes them in Postfix 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

Yep, I like setting the service name to mailman3. I'll note that Ubuntu's Postfix-Dovecot package already has a service for mailman (i.e. 2.x) which uses postfix-to-mailman.py.

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.


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

The good news is that I think Mailman 3 is getting more real every day. My

we had discovered and then we will work on the REST client/server.

I will update to the latest branch that should fix the language file problem

Thanks Patrick,
-Barry

Excellent! I forgot that one other thing must happen before 3.0 can be released; we need a migration script from 2.1.x to 3.0. I'll update the wiki page and release 3.0a4 a little later today. Then perhaps other folks can try the LMTP connection on other *nix distributions.

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