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

Rapidly switching between two mailboxes will cause a loading skeleton to be shown each time. However, once a mailbox has been opened it should be cached in the frontend.

Describe the solution you'd like

Only show the skeleton the first time when a mailbox is initially loading. The list should be rendered instantly on the second open. Loading fresh emails should happen in the background and not prevent the envelope list from being rendered.

Describe alternatives you've considered

No response

Additional context

No response