Re: Unseen attribute doesn't get saved in rmail

[Eli Zaretskii <eliz@gnu.org>]

> From: "Andrea G. Monaco" <andrea.monaco@autistici.org>
> Date: Mon, 11 Jan 2021 13:28:30 +0100
> 
>   > I'm asking why is it important for your purposes to know whether the
>   > mail was read for the first time or not.  Because if it isn't very
>   > important, the solution I proposed should work for you.
> 
> My mailboxes get pretty big, some gigabytes usually, so saving the
> buffer takes some seconds. I only want to save it if it got modified, for
> example because I read some messages for the first time and thus changed
> their unseen flag.

I see.

>   > That's the reason Rmail doesn't already have the feature you
>   > want: I guess no one else uses it as you do
> 
> Some features are more or less used than others. But saying that some
> use case is completely nonexistent is pretty strong: can you
> substantiate this claim?  Unless you are arguing that a feature being
> absent means that no one wants it: I would obviously disagree with that
> claim.
> 
> There's at least one person (probably more) who is unhappy with that
> behavior of rmail, and that's me.

Please don't interpret "no one" too literally.

The reason we don't already have this is that your use of the inbox is
unusual, and doesn't really scale well: once you hit gigabyte-level
size, you risk bumping into a situation where you don't have enough
memory on your system for Emacs to visit the inbox.  And, as you say,
you already suffer from prolonged save times.

That said, I won't object having a feature that will allow you to use
Rmail that way, so please feel free to submit a feature-request bug
report using "M-x report-emacs-bug".