Re: [PATCH v3] Allow applying filters to summary consecutively

[Eli Zaretskii]

> From: chad <yandros@gmail.com>
> Date: Wed, 23 Nov 2022 15:57:39 -0500
> Cc: Gregory Heytings <gregory@heytings.org>, andrea.monaco@autistici.org,
>  emacs-devel@gnu.org
> 
> FWIW, many years ago, I had to switch from RMAIL to mh due to some of the 
> factors Gregory mentioned,
> especially infrequent but troublesome corrupted rmail files and problems with 
> multiple concurrent clients.
> These problems are rare when users only use a single device to read from 
> local storage, but even 25 years
> ago I was using multiple geographically separated computers and shared 
> networked storage. RMAIL also
> suffered, performance-wise, as email volume increased. Certainly, some of 
> these problems were more due
> to movemail than BABYL.

Rmail's treatment of mbox files and the way it stores processed email have
been completely redesigned and reimplemented since the time you used it.  In
particular, Rmail no longer uses BABYL format, and doesn't rewrite the
incoming mbox stuff at all, but just processes it in-place using
buffer-swap-text.  The move to Unicode in Emacs and years of cleaning up the
code which encodes/decodes non-ASCII also contributed to solving many
problems.  So now Rmail has none of the problems that probably caused you to
switch from Rmail.  I use it every day, including to read and reply to this
email.

> That said, I think the existence of very old email clients such as nmh (and 
> mh-e) and alpine/mutt and newer
> clients such as notmuch and mu/m4e provide enough alternatives to rmail that 
> (I suppose) the interest in an
> updated rmail is very small.

I don't have objections to adding maildir support to Rmail, I just don't
quite see how that could be done without coding a complete new backend, or
even redesigning (again) how Rmail processes and presents email.  The
backbone of Rmail is a single mbox-formatted buffer which Rmail narrows to a
message it displays, and whose text it swaps with the display buffer using
buffer-swap-text, or reshuffles when some sorting is required, or searches
through when the user issues an Rmail search command.  To use maildir
without changing this basic design, Someone would have to find a way of
presenting multiple files in multiple directories as a single large buffer.
That should be possible, but the naïve ways of doing so will probably be
kludgey and unclean, let alone inefficient.