Is your feature request related to a problem? Please describe.

As a Nextcloud Mail user I want to get an overview of my inbox quickly. Looking at many unread messages can be overwhelming.

Describe the solution you'd like

Group and separate threads by the sort attribute (send date right now):

• Messages within the last hour
• Messages today
• Messages yesterday
• Messages last week
• Messages last month
• etc

When sorting by subject, the sections could be per first letter (A, B, C, ...), for message size in size groups (<10kB, 10kB-500kB, 500kB-1MB, 1MB+) and sender by sender email (alice@acme.org, bob@acme.org, ...)

Collapsing the sections is a nice-to-have but not required for the first version.

Describe alternatives you've considered

N/a

Additional context

N/a