Signal

An executive's inbox is where attention goes to die. He didn't need another email client — he needed someone else's judgment about what deserved his, delivered as a short list.

Any solution with its own database would drift from the truth of the mailbox within a week.

• Flag an email in the source inbox and it appears in the app on next load; live IMAP on every request, nothing cached, nothing to reconcile.
• Full messages render in a sandboxed frame with attachments; replies send through the real account with the right signature, quote and thread correctly, and file to Sent.
• Done (or a sent reply) clears the flag — 'dealt with' is a property of the mailbox, so it's true everywhere, forever.
• Whole-mailbox search across every folder, fanned out over ~8 parallel IMAP connections — 2–3 seconds typical.