How to access mailbox metadata in Lua push driver

Ralf Becker rb at
Mon Aug 3 19:15:28 EEST 2020

Making progress :)

I'll document some obtracles I found, to make it easier for the next one
implementing push with Dovecot and Lua.

First I tried with my usual Alpine based container, but Alpine seems not
to build the Lua stuff for Dovecot :(

So I moved to an Ubuntu 18.04 based container and the official Dovecot
CE repo:

FROM ubuntu:18.04
RUN apt-get update && \
   apt-get install -y apt-transport-https gpg curl && \
   curl | gpg --import && \ gpg --export ED409DA1 > /etc/apt/trusted.gpg.d/dovecot.gpg && \ echo "deb bionic main" > /etc/apt/sources.list.d/dovecot.list && \
   apt-get update && \
   bash -c "apt-get install -y
CMD [ "/usr/sbin/dovecot","-F","-c","/etc/dovecot/dovecot.conf" ]

I had to install lua-socket, which is used by the example script and not required by dovecot-lua, which is ok, you just need to know.

Using Aki's code snippet as user=<metadata> lead to an other error:

Aug 03 14:54:15 Error: doveadm: lua: /usr/share/lua/5.2/socket/url.lua:31: bad argument #1 to 'gsub' (string expected, got nil)
Aug 03 14:54:15 Error: lmtp(<username> 38): lmtp-server: conn [1]: rcpt <username>: lua: /usr/share/lua/5.2/socket/url.lua:31: bad argument #1 to 'gsub' (string expected, got nil)

I'm now skipping the notification, if no metadata is set, like the OX
driver does:

function dovecot_lua_notify_event_message_new(ctx, event)
  -- check if there is a push token registered if (ctx.meta == nil or ctx.meta == '') then return end

Currently looking into the following questions:

- can I get the rfc 5423 type of event somehow (obviously I can set it
on the event myself depending of the function called)
- looking at the example code, it looks like it can be called for
multiple messages, when does that happen (LMTP send more then one)
- why is the mailbox status put into an other structure and send with a
different notifiction
- does anyone have a code snippet to send a JSON encoded message
(probably easy to figure out looking at Lua docu)


Am 03.08.20 um 11:56 schrieb Ralf Becker:
> Thanks Aki, I'll check it out :)
> Am 03.08.20 um 11:40 schrieb Aki Tuomi:
>>> On 03/08/2020 12:31 Ralf Becker <rb at> wrote:
>>> We're currently using the OX push driver, which is straight forward
>>> (simple web hook) and allows to store (multiple) push tokens of our
>>> webmailer direct in mailbox metadata.
>>> Only drawback is that it only supports new arriving mails in the INBOX,
>>> even mails moved via Sieve to other folders are NOT reported.
>>> Therefore we updated now to Dovecot 2.3(.10.1) to also get mails moved
>>> by user or Sieve scripts, deleted mails or flag changes.
>>> As far as I read the example Lua scripts and (a little) the Dovecot C
>>> code, the nice indirection of using mailbox metadata to a) enable push
>>> and b) store push tokens (modify reported user attribute with them) does
>>> NOT exist in the Lua driver by default.
>>> So my questions is: how can I access mailbox metadata from within the
>>> Lua script, to make eg. the example script behave like the OX driver
>>> with user_from_metadata set?
>>> I'm happy to update the Lua examples, if that's any help ...
>>> Ralf
>>> -- 
>>> Ralf Becker
>>> EGroupware GmbH []
>>> Handelsregister HRB Kaiserslautern 3587
>>> Geschäftsführer Birgit und Ralf Becker
>>> Leibnizstr. 17, 67663 Kaiserslautern, Germany
>>> Telefon +49 631 31657-0
>> Actually it does exist:
>> or
>> mailbox:metadata_get()
>> You get both of these objects from the push notification data, you just have to keep them in the context state. (See the example scripts)
>> function dovecot_lua_notify_begin_txn(user)
>>    local meta = user:metadata_get("/private/key")
>>    return {messages={}, ep=user:plugin_getenv("push_lua_url"), username=user.username, meta=meta}
>> end
>> Aki

Ralf Becker
EGroupware GmbH []
Handelsregister HRB Kaiserslautern 3587
Geschäftsführer Birgit und Ralf Becker
Leibnizstr. 17, 67663 Kaiserslautern, Germany
Telefon +49 631 31657-0

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