Why is something like Gmail an awful client and what does a great client have (or has not) that it doesn't (or does)?

Mutt/pine (or newer clients like sup/notmuch) are faster, handles quoting/threading better, allows decent keyboard operation and is workable with high-volume of email.

My biggest issue with Gmail (as someone who interacts with users of Gmail) - is that it generally breaks quoting and hides this from Gmail users with its magic conversation view.

Outlook(web) does atrocious top-quoting rendering it useless for mailing lists.

In general the web interfaces doesn't work well with hundreds/thousands of mails IMNHO.

They also tend to needlessly lean on html formatting rather than plain text - with things like "my replies in blue" - rather than just proper quoting.

Ed: in general I've just given up the idea that the average user has any hope of interacting well with email lists - which means such lists aren't useful for general discussion (but can still work for specialist groups like Linux kernel etc).

The conclusion being that one will need "something else" for a general audience.

Zulip might be a reasonable compromise.

>Outlook(web) does atrocious top-quoting rendering it useless for mailing lists.

The weirdly aggressive way people talk about top vs bottom quoting is probably one of the things turning new users away from mailing lists.

Maybe. I think the bigger problem is that there's no easy fix/recommendation to give new users; "stop using your propiatary group-ware that your company/organization pays for" isn't a great recommendation.

Gmail can't do basics properly like replying in the middle of a quoted text, etc. It shows you something relatively sensible, but sends completely garbled mess to the recipient.

Yeah, I don't quite get it. The problem with mailing lists is their fundamental design, not the clients for them.

Mailing lists aren't great, and neither is nntp. But mailing lists (and nntp) work fine with proper clients and some discipline/netiquette.

Sadly I don't think there is a reasonable way to introduce new users at this point - I'm not aware of any great gui clients that do the right thing; and AFAIK neither Gmail or o365/exchange work in a reasonable way with open standards (allow checking for when others are free; accepting/changing appointments etc) - so users are herded towards the semi-proprietary clients. (and interop across silos doesn't really work in a sensible way).

There are things like the d-lang forums that mix a decent web front-end and nntp (and mailman makes an effort for web+smtp) - but I'm not aware of anything that really works great, with a low barrier of entry and reasonably lets users participate across more than a handful of threads.