You should be able to set `notmuch-search-oldest-first` to nil, either
manually or in the Customize menu.

Laurence Rochfort <laurence.rochfort@gmail.com> writes:

> Hello,
>
> In the notmuch emacs client, messages are always shown oldest at the top
> and newest at the bottom. This seems to be the case for both search results
> and when viewing a message content.
>
> How can I set the default to be newest first in all cases?
>
> Cheers,
> Laurence.
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