There are a few requests to be able to sort messages by date, subject, and sender.
This would probably require us to implement Make Threading/Conversation View Optional first. However, Gmail does allow sorting threads by date of most recent message; other clients allow sorting threads by original subject or original sender.
(Original issues had 14 votes in total.)
Installed Mailspring today, and will have to uninstall, I’m afraid. 
No way to sort inbox is a dealbreaker for me. Especially being unable to sort by date, so now I see emails in reverse order. It’s the only email client I’ve seen that can’t sort inbox, and it’s kind of baffling. I upvoted this request, but from the look of things this won’t be implemented anytime soon. Sorry, I really wanted to love it.
Same here. I’m looking for a new client to replace Postbox or Thunderbird, and Mailspring has the most promise so far. But missing basic sorting is a real head-scratcher. I won’t be able to use it on a daily basis without that.
I’m looking for this feature too. Unless I’m expecting something urgent in my inbox, I really like to have my list sorted by date from oldest to newest.
Apple’s Mail.app allows threading and sorting independently. Threading is a grouping feature where the most recent message is used for sorting parameters (at least with respect to dates, and sender, I believe). If messages are sorted by flag (star) and threading mode is enabled, then if any of the thread’s messages is flagged, the thread is treated as flagged. It’s actually really, really useful.
In other words (at least as best I can tell), threading is used to group messages and then sorting applies to the group as if it were a single pseudo-message (with varying behaviors regarding what comprises that pseudo-message from its members)
I need to have sort options for the inbox and folders.
Have created a PR with support for this request, no message/thread optional (though I think this should be implemented)