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nngmail

Introduction

nngmail is a Gnus back end for reading email using the Gmail REST API. If you read email with Gnus and use a Gmail-hosted account, you can use nngmail instead of nnimap. nngmail does not act as a transport agent. Sending and replying to email will continue to use whatever method you have setup in Emacs previously.

nngmail does not access the Gmail servers directly. Instead it relies on a local server (or proxy) that stores message metadata and caches some messages in a local sqlite database. Because Gnus can access data locally, reading mail is instantaneous. Synchronous requests to Gmail are required for:

  • Reading a message that is not in the local cache
  • Searching your email

Synchronization happens via polling (the polling interval is configurable). Cached messages are zipped before storing them in the sqlite database to save space.

The local server can sync multiple Gmail accounts simultaneously. You access them by setting up multiple servers in Gnus. The proxy does not (currently) provide for real synchronization support in offline mode (see Destructive mode below)

While the local proxy is meant for use with the nngmail back end, it provides a generic REST interface for reading messages that may be of use for other tools. For example, it may be interesting to generate an email dashboard. In a pinch, you can read your mail by simple running sqlite!

Status

I use this on a daily basis but you should consider it "me-ware". I am not adverse to it becoming "us-ware" but that's not what has driven the effort. I wrote it in a bit of a hurry as I was more interested in how much work would be required to write a new Gnus back end. Now that I have convinced myself it is a possible and worthwhile effort, I will go back and develop a test suite before adding more features. Plus setup is a bit involved--you need to be comfortable with shell, python, and Emacs.

This software will not eat your mail no matter how hungry it is. By default the system requests read-only access to your Gmail account. The Gmail API service will thus deny requests to modify or delete messages (if it doesn't, something is seriously wrong).

There is experimental^2 support for updating and deleting messages in the destructive branch. Use with caution, it may well eat your email.

Once there is a nice test suite, I will enable write-mode by default. Until then, you will have to opt-in to life on the edge.

The local proxy stores the name and email of everyone you correspond with (so you could use it as a local address book). But it is rather simplistic in how it handles multiple email addresses and names. This can cause the From field to appear a bit funny at times. For example, if a company changes how they send email notifications (I have seen this with old LinkedIn messages).

Emacs & OS Support

I use this code on Ubuntu (16.04 LTS and 18.04 LTS) and OSX (10.12 and 10.13) on Emacs 25.3 and 26.1. I haven't tried running it on Windows (and probably won't). Patches for older/newer versions of Emacs are welcome.

Security

The server responds to un-authenticated http requests and makes no attempt at preventing unauthorized access to your email. The only (small) nod at security is to listen on the local interface only.

Documentation

Yeah, as you guessed there is no documentation other than this README file.

There are a number of configuration options which you can tweak. See data/config.yaml for some. There is support for parallel requests when importing an account. However, it does not yet handle errors due to too many simultaneous user requests so it's best to leave the setting as is.

Motivation

I wrote this because I was frustrated with how long it takes to read email with Gnus. My mail reading was state-of-the-art 30 years ago but it feels like it hasn't improved with time (although it clearly has). My main frustration was how long it takes to check for new messages. And so I wanted a system that would allow me to read email quickly and with low overhead. In particular, I want:

  • Fast access to recent email
  • Fast and accurate search for everything else
  • Use Emacs to compose email

I tried offlineimap and notmuch but neither was what I am looking for. I don't want to keep an complete copy of all my Gmail accounts on my laptop (someday this may not be a problem but right now it requires a significant fraction of available storage). Plus I find search works best in Gmail because it searches through attachments.

Which brings up the topic of why Gmail since we should be wary of providing Google too much of our personal and private information. This is absolutely true. However, when I looked at all the email I received, a significant portion of it either originated from or was delivered to Gmail anyway. That is, even if I move my account elsewhere Google will still have my information. Furthermore, sometimes you are forced to use Gmail, e.g. for a work account.

When I do move elsewhere, I think the system should be easy to extend to other mail service providers.

Installation

  1. Clone this repo

  2. Enable Gmail API access for your account (this may be a bit out of date).

    2.1 Visit the [Google Developer Console] (https://console.developers.google.com/). From there, you need to create a project (or choose an existing one) and go to the APIs section. Choose “Gmail API” under the Google Apps APIs section and click the “Enable API” button.

    2.2 Go to the [Credential page] (https://console.developers.google.com/apis/credentials) and click Create credentials > API key and select the appropriate key type.

    2.3 Store the credentials under data/client-secret.json. If you choose a different location update the config.yaml file.

    Please see the instructions on the Using API Keys section of the Gmail API documentation if you have questions.

  3. Setup the local server

    3.1 Create a new virtual environment (virtualenv). I recommend pyenv to set this up, but virtualenv works well too.

    3.2 Install nngmail by running

     cd <repo>
 pip install -e .

    3.3 If everything was installed correctly you should be able to run

     FLASK_ENV=development FLASK_APP=src/nngmail:app flask routes

 And see a list of routes for the proxy server.

  4. Import your mail.

    4.1 Create the database with

     FLASK_ENV=development ./nngmail.sh init-db

    4.2 For each account you want to sync locally run

     FLASK_ENV=development ./nngmail.sh import [email protected] nickname --init-cache

    Where you clearly need to replace your user name and the nickname. You will be directed to a web browser where you need to login to Google and authorize the application (nngmail or whatever you called it in step 1) to access your mail. In some instances (I have only seen this on Ubuntu) you will be asked to copy-paste a URL into your browser.

    Pick a different nickname for each account as you will use it to identify the accounts to Gnus.

    If things went as expected the client will start synchronizing your email. By default it will download all message metadata and cache messages received by the Gmail SMTP servers in the last 120 days (edit config.yaml to change cache retention timeout). If cache_timeout is set to 0 it will not cache any messages. If set to -1 it will cache all messages.

    Initial synchronization time depends on how much email you have. For me it processes about 100 messages/sec. YMMV.

    Repeat the import command once for each account you want to synchronize/read via nngmail.

  5. Configure Gnus to read mail via nngmail.

    5.1 Load nngmail.el into your Emacs session. For now M-x find-file RET elisp/nngmail.el and then M-x eval-buffer.

    5.2 Configure one virtual server per account. Add something like this to gnus-secondary-select-methods. You need one server per account

     (nngmail "personal"
 	 (nngmail-email "[email protected]")
 	 (nngmail-address "localhost")
 	 (nngmail-server-port 5544)
 	 )
 (nngmail "work"
 	 (nngmail-email "[email protected]")
 	 (nngmail-address "localhost")
 	 (nngmail-server-port 5544)
 	 )

    The virtual server name (personal, work in the example above) and the email address must match what you used in the command to import the account.

    Don't forget to eval the assignment to gnus-secondary-select-methods.

  6. Subscribe to new groups in Gnus. The local proxy presents each Gmail label as a newsgroup you can read with Gnus (similar to how the IMAP interface works). If you open server mode (with ^ in the group buffer) you should see one server per nickname (or account). If they are not listed as opened something went wrong.

    Because by default nngmail request read-only access to your account(s) messages will not be marked as read permanently (they are marked as read until you check for new news).

  7. Setup fast access via helm. This package also provides a helm source you can use to read/deal with email (still a bit incomplete). My goal is to provide a quick mechanism for reading and processing email without having to open Gnus. To try this out load helm-nngmail.el and then run M-x helm-nngmail. It will show you unread messages in all your accounts (beware if you keep a large number of unread messages in your mailbox). You can select one or more messages to process and typing filters the list of messages. Use prefix-arg to select a different label to process.

    The helm interface is still in it's infancy, but I have great hopes for what it can do.

Details

One challenge with using Gnus and Gmail is Gnus requires nice monotonically increasing article ID's--preferably without too many gaps. The need for a local database arose from having to map from a Gmail message ID to something that looks like an article number.

In the database each message is tracked via an id, an article_id, and account_id. The id is unique across accounts--it's the primary key of the SQL table. article_id is unique within an account and is the article number passed to Gnus. Each row in the table stores the Gmail ID required to talk to the Gmail API.

The local server provides a very simple interface for accessing the local sqlite database. And it acts as a proxy for the Gmail API. That is, the nngmail lisp code never talks to the Gmail API directly. The proxy server runs a background thread per account to periodically poll for changes.

Searching (via nnir in Gnus) allows passing arbitrary Gmail search strings. The query is further limited by the group (or label) that nnir is trying to search (see the documentation for nnir for more details). Because the query is passed as-is to Gmail, you can use the usual Gmail search tricks.

The synchronization does not exports Gmail-assigned category labels, like CATEGORY_PERSONAL, as groups. Although there are hooks to export them if someone really wanted to.

Performance

I haven't done performance testing, but subjectively there is a world of difference between using nnimap and nngmail due to the local cache. On my i7-5600U-based laptop (8G of DRAM) I can comfortably read folders with 5000 emails (Gnus will show the Summary buffer almost instantaneously).

Selecting "articles" (in Gnus parlance) which are in the local cache should be almost instantaneous. Selecting articles not in the cache will synchronously request the message from Gmail using the REST API.

I believe Gnus has support for locally caching articles and such. But I have never been able to make it work. Plus sqlite is a much better store engine.

Destructive mode

To enable destructive, a.k.a. read-write mode, edit the data/config.yaml file to add the modify scope. The scopes section should look like this

scopes:
  - https://www.googleapis.com/auth/gmail.readonly
  - https://www.googleapis.com/auth/gmail.modify

Note that the refresh token used to authenticate you remembers the original scopes not the currently requested scopes. If you initially logged into Gmail using read-only mode, you will need to delete the credentials file (data/<account-email>-creds.json) and re-authorize the application to access your account. Furthermore, you will need to either re-initialize and re-import your email or hack the SQL to make the accounts writable.

Please note the same applies when going in the opposite direction. If you want to try out destructive mode and you add modify scope in config.yaml, please remember to delete data/<account-email>-creds.json and re-authenticate.

If you enable destructive mode Gnus marks get propagated to the server for posterity.

Note that the local proxy does not support offline mode. It relies on synchronous calls to Gmail to update state. I may someday implement support for offline mode so marks set while Gmail is not reachable will be synchronised next time the API is available, but it is not a goal at the moment. It may be possible to get Gnus caching to work with nngmail to enable offline access but I haven't tried.