My Personal Information Filtering System Design

Rmail is a built-in MUA for Emacs. It seems not used by most of the community, so I did not consider it as a choice from the beginning.

Gnus is a all-in-one client, which is famous for its slowness (not a big issue with local mail server set up as (Chamberlin 2023)), difficulty to set up, and crazy rich of feature sets as (Bin 2014; voltecrus 2018) suggest.

It is more like a front-end to news group rather than a front-end to email, and is greater at handling mailing list rather than individual personal back-and-forth conversations.

• It is integrated into Emacs ecosystem already, because it is a built-in
• It is able to handle Emails (mainly for net protocols I think, although Maildir is also supported)
• it does not handle ATOM feed due to its age, but there is an extension addressing this.
• It is easy to handle many kinds of web updates with Shimbun, and also it supports some good old solutions like nntp.
• It has scoring, and many other extensions to prioritize the inputs.
• It does not do offline caching out of the box I think, but with an external Maildir set-up at least emails are pre-fetched.
• the interface is definitely unified.
• it blocks heavily when refreshing, so people in communities usually run it in a separate Emacs instance. This is not a big problem with a local email server. See (Purcell 2010).
• It use eww to display contents.
• It is not remotely accessible.
• It is not accessible from mobiles.
• It does not have built-in support for as-is permanent archive, but should be easily extensible.
• It's Emacs built-in, I think it is standardized.

wanderlust is Another all-in-one client, maintained by the community. It is on top of w3m instead of Eww. Its documentation is really out-of-date, but actually it is still maintained. There are (LdBeth 2017a; Fu 2018) to give views on a subset of its functions. The author of Mu4e also has some (old) write-ups about it: (Binnema 2011, 2009b, 2010, 2009a).

• it is not integrated as deeply as Gnus, but still it is Emacs!
• It has decent Email support, including net protocols and Maildir.
• It can handle Feeds
• it also has Shimbun support (and I think this integration is the best among all the supported client)
• It has mu and Notmuch supports to filter the inbox.
• it has support for Maildir, and it can even cache things by itself.
• The interface is mostly unified.
• it blocks when refreshing, but with supports of Maildir it is okay
• it use W3m to display things
• It is not remotely accessible.
• It is not accessible from mobiles.
• It does not have built-in support for as-is permanent archive, but should be easily extensible.
• It is not Emacs built-in, and it has its own MIME/CL-like/web libraries, so it is not that standardized.

mu4e is a dedicated MUA on top of mu, a Xapian based text indexing tool that focuses on searching. Its UI is said to be more Emacs-ish according to (Jie 2019; Wellons 2013). It is a popular new MUA implementation in the ecosystem, as (Snader 2023, 2015; Lafon 2023; Bertrand 2021; Maughan 2015) suggests.

• It is much more light-weight than Gnus or Wanderlust, makes it easier to integrate with other code.
• It depends on Maildir
• It cannot handle feeds. But we can have external tools to work around it.
• It cannot handle other web updates. But we can have external tools to work around it.
• It uses mu to filter by searching.
• It relies on Maildir, so yes
• Since it does not support Feeds and other web updates natively, we need some hard work to make the interface unified
• Maildir is updated by external tools, so there is no refreshing overhead in mu4e.
• In the email list it does not have collapse feature built-in, so mails of the same thread take several lines. it reuses Gnus' gnus-article-mode (with a derived mode) to display messages. So everything that works for Gnus should work for it too. This also means that only one post in the thread is displayed instead of a whole thread (like Notmuch).
• It is not remotely accessible, claimed by (Wellons 2013).
• It is not accessible from mobiles.
• It does not have built-in support for as-is permanent archive, but should be easily extensible.
• It is not Emacs built-in. It mainly depends on Maildir standard only(with mu as a searching tool), as (Nelson 2015) hints, so it integrates with other tools.

Notmuch is a dedicated MUA on top of notmuch, a Xapian based text indexing tool with the same name (which makes search engine unhappy) that focuses on tagging. I actually used notmuch (the searching back-end) with mutt as the front-end several years ago when I was still using Neovim, and the experience was great. It is also quite popular in the ecosystem, as (Zakkak 2021; Sapka 2023; Siewierski 2019; Korytov 2021) suggests.

• It is much more light-weight than Gnus or Wanderlust, makes it easier to integrate with other code.
• It depends on Maildir
• It cannot handle feeds. But we can have external tools to work around it.
• It cannot handle other web updates. But we can have external tools to work around it.
• It uses notmuch to filter by tagging.
• It relies on Maildir, so yes
• Since it does not support Feeds and other web updates natively, we need some hard work to make the interface unified
• Maildir is updated by external tools, so there is no refreshing overhead in notmuch. (tohiko 2021) says it is faster than mu4e.
• It has a thread-based message view, quite like Gmail. It uses Eww to display the HTML contents.
• It can be accessed via SSH, claimed by (Wellons 2013).
• It is not accessible from mobiles.
• It does not have built-in support for as-is permanent archive, but should be easily extensible.
• It is not Emacs built-in. It saves tags in a separate database (while keep the Maildir mostly immutable), as (Nelson 2015) hints, so it is harder to integrate with other tools than mu4e.

Elfeed, different from the above ones, is an RSS client, and it is said to be inspired by Notmuch. It is also very popular in the community, as (Cundy 2022; Liujacai 2021) show.

• It is much more light-weight than Gnus or Wanderlust, makes it easier to integrate with other code.
• It depends on Maildir
• It cannot handle feeds. But we can have external tools to work around it.
• It cannot handle other web updates. But we can have external tools to work around it.
• It uses notmuch to filter by tagging.
• It relies on Maildir, so yes
• Since it does not support Feeds and other web updates natively, we need some hard work to make the interface unified
• Maildir is updated by external tools, so there is no refreshing overhead in notmuch.
• it use Eww to display the contents.
• It can be accessed via SSH, claimed by (Wellons 2013).
• It is not accessible from mobiles.
• It does not have built-in support for as-is permanent archive, but should be easily extensible.
• It is not Emacs built-in. It saves tags in a separate database (while keep the Maildir mostly immutable), as (Nelson 2015) hints, so it is harder to integrate with other tools than mu4e.

Offlineimap fetches emails from servers into Maildir folders. It is implemented in Python, so its performance might not be that great. Its configuration can basically invoke most kinds of Python code.

mbsync fetch emails from servers into Maildir folders. It is implemented in C.

Dovecot is a local email server.

feed2maildir is implemented in Python. There is also a fork (Warburton 2017) that makes it fits more into the Unix Philosophy: do one thing, do it well.

The upstream implementation uses a database to save information about last checked time for each feed, and converts each item directly into a Maildir file.

imm is implemented in Haskell. It saves information about feeds in a database, and make callbacks (with JSON intermediate) to external tools. It comes built-in a tool that sends emails, and there is no direct Maildir support.

feembox is implemented in Rust. It saves items to Maildir files directly, and it seems to not have any database saving the progress for each feed.

ua is implemented in Go. It has a bunch of executables, mostly following the Unix Philosophy:

• a cron-like timer
• a tool to fetch new items
• a tool to convert new item into Maildir file

Shimbun is basically a web scraper interface implemented in Emacs. See (LdBeth 2017b). It is part of W3m, and there is already Wanderlust and Gnus integration.

RSSHub is an "extensible RSS feed aggregator" which can be deployed privately.

rss-bridge is a "PHP project capable of generating RSS and Atom feeds for websites that don't have one."

huginn is a really all-in-one web automation written in Ruby, like a private version of IFTTT. See (笠三叶 2015). I'd say it looks scarily feature-rich.