Improve the inbox experience through expanded notification settings and better message handling behavior.
Overhaul message threading so each message can be acted on separately.
Allow threading to span inboxes.
Reply-to: offer in composer and honor in reply.
Per-account and per-folder notification settings.
Muting and per-account notification scheduling.
Improve folder management UX.
Allow moving messages between accounts.
User-defined mail storage settings (per account/folder?) and server ping frequency.
Allow users to select default actions and on-message action buttons.
Allow disabling IMAP or SMTP for an account.
(Proposed) Support IMAP-based message labels.