Is your feature request related to a problem? Please describe.
Unless I'm missing some option/configuration I can't see a way to disable grouping of emails (last hour, today, yesterday, last week, etc.). While I guess it is something that is desirable for many, it is not for many others.
Related to this I would also suggest to show in more clear way the date/time of the emails in the split screen/list views (with attention also to the alignment), i.e.
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Describe the solution you'd like
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Describe alternatives you've considered
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Additional context
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