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Gmailctl – Declarative Configuration for Gmail Filters (github.com/mbrt)
155 points by tbodt on March 29, 2020 | hide | past | favorite | 21 comments

This is interesting; what benefit/advantage does it have over IMAP-level email management tools like imapfilter[1]?

I don't ask that to be confrontational; I've successfully managed several email inboxes on several different providers for years with plain old IMAP rules, so I'd like to know if there's anything I'm missing.

[1]: https://github.com/lefcha/imapfilter

You offload all the processing to the gmail backend? No compute needed on your part?

I made something like this a while back for myself, and it worked all right, but I ended up never even using it myself. The main problems I had were:

- You end up with multiple sources of truth for what's happening to your email. And/or you won't be able to easily edit your filters from multiple machines.

- Either the source code or the generated code ends up being hard to read.

- There's imperative (and sometimes counterintuitive) behavior in Gmail regarding labels, and that can interfere with declarative reasoning.

- Filters have a size limit! So you might need to take that into account if you have complicated filters.

`gmailctl` resolves a few of these, actually. The big one is that there's a command to diff your config file with what's in gmail, so you can capture any accidental changes that happen in gmail-land. This also helps with version-controlling your configuration, since it shows you when you just forgot to upload your config.

The imperative behavior and filter size limits are still annoying, granted. You can deal with it by staging through multiple labels, but it's not great.

Oh cool! Version control is useful. I might give it a shot sometime. I didn't have anything of the sort.

If you're curious, the tool I came up with had a DSL like this:

  $excom = from:example.com
  $exorg = from:(example.org OR example.net)
  if ($excom AND $exorg) AND -(to:me OR in:spam)
    if cc:person
      label "Person"
and it'd auto-translate to this:

  <?xml version='1.0' encoding='UTF-8'?>
  <feed xmlns='http://www.w3.org/2005/Atom' xmlns:apps='http://schemas.google.com/apps/2006'>
      <category term='filter'></category>
      <apps:property name='hasTheWord' value='(from:example.com from:{example.org example.net}) -{to:me in:spam}'/>
      <apps:property name='shouldArchive' value='true'/>
      <category term='filter'></category>
      <apps:property name='hasTheWord' value='(from:example.com from:{example.org example.net}) -{to:me in:spam} cc:person'/>
      <apps:property name='label' value='Person'/>
which it would translate back to this:

  if (from:example.com from:{example.org example.net}) -{to:me in:spam}
  if (from:example.com from:{example.org example.net}) -{to:me in:spam} cc:person
    label "Person"
It didn't treat the filter as a blob (it actually parsed it and removed quotes etc. if appropriate) but it also didn't really change the underlying language either.

But it had variable and did let you nest conditions which made it easier to write some things. (Or so I hoped. In the end I didn't feel it was worth it...)

Another advantage of gmailctl is it uploads the filters using the API, so you don't have open Gmail settings and manually import an XML file.

You can technically get around the filter limit by switching from filters to Appsv Script. Setup a staging inbox, then run the query and action rules against that stagig area every 1 to 5 minutes.

I've considered that for a long time, but the trouble is it's not as robust, not to mention there's also a script time limit which I would hit as a result of having other scripts...

Huge respect to the author for ealizing this - however, I'm honestly sceptical of including yet another turing-complete configuration DSL without sufficient debugging capabilities.

Seems to me, now you've added several more sources of complexity:

- You have to get the JSONnet syntax right and learn about th various functionalities and expressions.

- You have to ensure Jsonnet is correctly translated into the GMail filter chain.

- You still have to ensure the GMail filter chain works correctly - this is one of the original problems this project set out to solve, but I don't understand what additional tools the project gives you to archieve this.

Author here. I understand your concerns, and in fact one of the last things I added is unit tests: https://github.com/mbrt/gmailctl/blob/master/README.md#tests

Getting things right is not easy, especially in complex languages like jsonnet. In my own experience though, every time you limit the expressivity of config languages you end up inventing even more complex workarounds in the end (e.g. external templating and things like that).

I use something like this that a Googler shared with me.

It's super helpful to get around the way Gmail doesn't really let you order rules.

This helps you generate mutually exclusive rules, so the ordering doesn't matter.


The real benefit Gmail has over most other email solutions, including Outlook, is labels for emails which are like virtual mailboxes. Almost all IMAP-based solutions I've seen don't attempt to solve this problem, which is why people keep using Gmail. If something like this was automated through Dovecot, people would be much more likely to host there own email.

That's a pretty awesome project! I wrote something to automate label manipulation too, but I used a simple scripting language.

I migrated from self-hosted mail where I had the power of procmail, to gsuite, where I had less flexibility. Making simple filters via the google UI is easy, but it gets complicated when you want to look at both the subject and the sender - to file "Facebook comment replies", "Facebook messages", and "Facebook event invitations" under different labels for example.

It's a pain to authenticate, but once that's done I like my solution. Downside is you need to run it under cron:


The appeal of this gmailctl is that it keeps everything native, and doesn't require a server to run a cronjob. Nice work.

I wonder if a terraform provider for gmail would make sense.

I have one that I've been using for some time now: https://github.com/remilapeyre/terraform-provider-gmail

It should work without issues, I need to document it though. Let me know if you have some troubles using it.

Oh well, I pretty much did the same thing at the same time! Albeit with some tests/docs :D https://github.com/ndrpnt/terraform-provider-gmail

If the author comes along, are there any plans to support FastMail for those of us who don’t use Gmail? I’d be willing to pay a bounty.

Fastmail already supports Sieve, so I'm not sure you'd need something like this.


TIL! Thank you kind stranger.

Nice tool. Pretty popular at my workplace.

F### GMail.

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