macOS & Windows · Microsoft 365, Gmail, Proton & Zoho · Built in Rust

Classic Outlook,
rebuilt to be fast.

DPKooltuo works the way classic Outlook does, with the same ribbon, folders, shortcuts and habits. It fixes what people complain about most: slow search, painful shared mailboxes and a cache you can't control.

Mac 0.3.6 · Windows 0.3.6 · macOS 11+ (Apple silicon and Intel) · Windows x64 · All downloads

DPKooltuo main window: the Inbox in splits, a drafted reply and quick replies above the open message, and the Upcoming pane with meetings and likely events on the right
0 ms38 results across every mailbox, from the local index
13 msto run rules over 2,650 messages
3mailboxes side by side, each with its own cache
1 languagefor search, smart folders and rules
Shared mailboxes

Every mailbox gets its own pane, its own cache and its own sync.

Open your Inbox, the help desk and billing side by side, in tabs and split panes. Unread counts and sync status are per mailbox, and one All Inboxes view merges them.

  • Add a shared mailbox in seconds, with no profile rebuild and no restart
  • Choose how many months each mailbox keeps offline
  • Sync or rebuild one mailbox without touching the others
  • Send as the shared mailbox; the copy lands in its Sent Items, not yours
  • Saved views: name a layout of tabs and panes, then switch to it from the folder pane
  • Settings sync: rules, tags, smart folders, auto labels and saved views follow your Microsoft 365 account to your other computers. Mail never leaves your machine for this, and you can turn it off
Three inboxes side by side in split panes, with saved views in the folder pane
A saved view: all mailboxes side by side
Mailboxes and cache settings with per-mailbox cache window, sync and rebuild
Per-mailbox cache window, sync and rebuild
Work week calendar overlaying three mailboxes' calendars
Calendars from every mailbox, overlaid
Smart folders

Saved searches that span every mailbox.

Write a query once and it becomes a folder with a live unread count. "Needs attention" across your Inbox and two shared mailboxes is one line:

(is:flagged OR is:important) -is:complete
  • Live match count and preview while you type
  • Save any search as a smart folder in one click
  • Open a smart folder in its own pane
  • Turn its conditions into a rule
New smart folder editor with conditions, insert chips and a live list of matching messages
A live match count and preview, across all mailboxes
Rules

Rules built on the same query language, running locally or on Exchange.

Move, archive, delete, mark read, flag, categorize, forward, silence notifications or stop processing. The editor shows which recent mail would match before you save.

  • DPKooltuo rules handle what Exchange can't: flags, dates, read state, any shared mailbox
  • Exchange rules run on the server, even with your computer asleep, and show up in Outlook
  • Rules made in Outlook appear too: toggle, delete, or manage them here
  • Hit counts and a recent-activity log for every rule
Rules window with local and Exchange rules, other Exchange rules and recent activity
Local and Exchange rules in one list
Rule editor with mailbox scope, conditions, live preview of matching messages and actions
Right-click a message ▸ Create rule…
Command palette filtering commands and folders
Every command and folder is a ⌘K away
Tags & folders

Tag anything in a keystroke. Organize with real folders.

Tags are Outlook categories with any name and any of Outlook's 25 colors, so they show up in Outlook too, and your tag list stays in sync with it.

  • Ctrl+T to tag: type to filter, Enter to toggle, or create a new tag on the spot
  • Drag messages onto a tag, or use the Tag menu on any message
  • Every tag is a view with unread counts, across all your mailboxes
  • Create, rename and delete folders in any mailbox, including shared ones (Ctrl+Shift+E)
Tags settings with names, colors and message counts, and the Tags section in the folder pane
Name and color your tags; they stay in sync with Outlook
New folder dialog with mailbox and parent folder pickers
New folders in any mailbox
Rules window
Rules can tag mail as it arrives
Reminders & sending

Deal with it later, without losing it.

Press H on a message and pick a time. It leaves your inbox on every device and comes back, unread and at the top, when you asked for it.

  • Pick a preset or type a time: 2h, fri 9am, tomorrow 3pm, nov 20
  • Reminders return under their own heading, with a notification, even when the app is closed
  • Undo send: a few seconds to take a message back, with the draft reopened exactly as it was
  • Send later: schedule a message, then edit, cancel or send it now from the Scheduled list
Remind me picker with presets from Later today to In a month
H: remind me later
Sending toast with an Undo button, above a reminder toast
Undo send, and a reminder coming back
Inbox with a Reminders group at the top of the message list
Reminders come back at the top of the inbox
Writing

Format a message properly, and say the usual things in one keystroke.

New messages and replies have a formatting toolbar. What you write is sent as ordinary formatted email, so tables, lists and code look right in Outlook and Gmail.

  • Bold, headings, lists, quotes, links, code blocks and tables, by button, shortcut or typed Markdown
  • Preview shows the message as the recipient will see it
  • Snippets: reusable text with fill-ins like the recipient's first name. Type ;thanks and a space
  • Share a folder of snippets with your team
  • Insert my availability lists your free slots from the calendar
Compose window with the formatting toolbar and a message written in Markdown
Toolbar, shortcuts or plain Markdown
Snippets settings with a list of snippets, shortcuts and fill-in variables
Snippets with shortcuts and fill-ins
Sender card with mail counts, recent messages and quick actions
Click a sender for their history, meetings and quick actions
Inbox on autopilot

Sorted, drafted and followed up for you.

The inbox arrives in splits, replies are waiting for your review, and anything nobody answered comes back on its own. The AI features are off until you turn them on, and nothing is ever sent for you.

  • Split Inbox: Team (your own email domain), VIP, one split per auto label, and Other. Collapse them to one row, or double-click a split to open it in its own tab
  • Auto labels sort new mail into Marketing, Cold pitch, Social, News, Receipts or labels you describe, and can mark it read or archive it
  • Auto Drafts prepare a reply in your own style for mail that needs one; Instant Reply offers three one-click answers
  • Remind me if nobody replies: the bell next to Send brings the message back in a day, two, three or a week
  • Ask AI (⌘J): ask a question about your mail and get an answer with links to the messages it came from
  • Team, automatic by email domain with Microsoft 365: optional read statuses, and conversations shared with comments
Ask AI window answering a question about audit evidence with numbered links to the source messages
Ask AI answers from your mail, with links to the messages
Reply window holding an AI-drafted reply, with the remind-me bell set to 2 days next to Send
A drafted reply to review, with a reminder if nobody answers
Productivity settings: Split Inbox, remind me if nobody replies, Auto Drafts and Instant Reply
Each one is a switch in Settings ▸ Productivity
Auto labels settings with editable labels, colors, descriptions and actions
Describe a label in plain words; choose what happens to its mail
Upcoming

Your day, next to your mail, including what isn't on the calendar yet.

A pane beside the workspace shows what's next with a countdown, then each day's meetings. Likely events mentioned in your mail sit in the same days, one click from your calendar.

  • Now and next: the current or next meeting, how long until it starts, and a Join button
  • Dense days: time, length, place and organizer on two lines, with overlaps and unanswered invitations flagged. Click an event for its details
  • From your mail: "Thursday at 2pm works", a meeting link with a time, "due by Nov 20", a maintenance window. Open the message, add it to your calendar, or dismiss it
  • The mail scan runs on your computer. No AI is involved and nothing is sent anywhere
  • Dock it right, left, top or bottom, or collapse it to a strip that still shows the countdown
Upcoming pane docked along the bottom: a next-up card, then Today, Tomorrow and Saturday as columns with meetings and likely events from mail
Docked along the bottom, each day is a column
Assistant

Summaries and drafts, on the AI your organization chooses.

Summarize a long thread, or have a reply drafted for you to review. Nothing is sent to the AI until you ask or turn on one of the background features, and drafts are never sent for you.

  • DPAI gateway: the models your organization and team make available, with its data protection and spending rules
  • Local subscriptions: Claude Code or Codex already signed in on your computer
  • API connections: your own Anthropic or OpenAI key
  • Guided setup checks each step of the connection, signs you in to the gateway or a subscription from a button, and tests it. With several Claude or ChatGPT accounts on one computer, it finds them and asks which to use
  • IT can limit the assistant to the gateway, or turn it off
  • Mailing lists get a one-click Unsubscribe and Block sender
  • Verified brand logos (BIMI) replace initials when a message passes DMARC: a thin gold ring when the logo is backed by a Verified Mark Certificate, grey when it isn't
Reading pane with a mailing list bar and an AI summary of the thread above the message
A thread summary, above the message
Draft with AI popup in the compose window
Say what you want; review the draft before you send
Assistant settings: DPAI gateway, local subscriptions and API connections
Choose where the assistant runs
Guided setup checklist for the DPAI gateway: DPAI found, sign in to your organization with a browser button, then the gateway and a test request
Guided setup finds the step that's stuck and offers the button that fixes it
Guided setup listing four Claude Code installs, including claude_personal and claude_work with the account each is signed in to
Work and personal accounts on one computer: it finds them and asks which to use
Background service & AI agents

Notifications when it's closed. An MCP server for your AI assistant.

A lightweight background service keeps mail syncing and raises notifications when the window is closed. When the app is open, the service pauses so nothing is fetched twice.

Built-in MCP tools let Claude and other assistants search and read mail, calendar, contacts and tasks, triage, draft replies, and create smart folders and rules. Sending stays off unless you allow it, and every change an agent makes is logged.

Background service and AI agents settings
Agents draft; you send, unless you choose otherwise
Under the hood

Native and local-first, built for speed.

One Rust binary with a GPU-rendered interface and a SQLite cache. Every change happens instantly on your computer and syncs to Microsoft 365 in the background.

DPXchange, Gmail, Proton & Zoho too

Add DPXchange (mail, calendar, contacts, tasks and shared mailboxes, with a password, a passkey or Microsoft 365 sign-in), Gmail, Proton Mail (via Bridge), Zoho Mail or any IMAP account next to Microsoft 365. Rules, smart folders, tags and search work across all of them, and DPXchange rules can run on the server, shared with DPXchange Mail.

Instant everywhere

Lists, search and counts come from the local index, so moves, flags and deletes take effect immediately, even offline.

Smart sync

Delta sync, batched requests and stable item IDs, with automatic back-off when Microsoft throttles.

Sign in with Microsoft

Browser sign-in with PKCE. No app registration for users to set up, and tokens are stored only on your computer.

Org-managed signatures

Your own signatures, or one pushed by IT through device management, with profile fields filled in automatically. Server-side signature tools are detected so you don't get two.

Panes, your way

Tabs and split panes, reading pane right, bottom or off, conversation view, compact density, and dark, light or system theme.

Safe by default

Remote images are blocked until you allow them. The Mac app is signed and notarized, and it updates itself only from signed releases whose downloads match a published checksum. Its local sockets are private, and agent actions are audited.

Light theme
Light theme
Compose window in Preview, showing the message as the recipient will see it
Compose from any mailbox, and preview what the recipient gets
Download

Get DPKooltuo

Free to install. Sign in with your Microsoft 365 account; in most organizations nothing else is needed. If yours requires admin approval, DPKooltuo shows the link to send IT.

macOS

DPKooltuo for Mac 0.3.6

One universal app for Apple silicon and Intel Macs on macOS 11 or later. Signed with a Developer ID and notarized by Apple, so it opens without warnings. From 0.1.6 it updates itself.

Download 0.3.6 .dmg · 35 MB
  1. Open DPKooltuo-0.3.6.dmg and drag DPKooltuo into Applications.
  2. Open it and choose Sign in with Microsoft.
  3. Optional: turn on the background service under Settings ▸ Background & AI agents.
SHA-256 a6fb3a5cce37ae2b0e8caa7cd62ef19b4594a013d985faeb8e8ce70f58ab9da6
Windows

DPKooltuo for Windows 0.3.6

For 64-bit Windows. Use the installer, or the portable zip if you can't install software. Installed with the MSI, 0.2.2 and later update themselves (on an older version, install this one once); the portable version is updated by downloading it again.

  1. Run DPKooltuo-0.3.6-win-x64.msi, or unzip the portable version and run dpkooltuo.exe.
  2. This build isn't code-signed yet, so Windows may say "Windows protected your PC". Choose More info ▸ Run anyway.
  3. Open DPKooltuo and choose Sign in with Microsoft.
MSI SHA-256 7e3959d4cb28de9acfa277de3b75651f981760ded6a738fe0736e3e2f3b42f3d
ZIP SHA-256 7ab0ed2bc58a98873a8ced17d8659ee79631bf35fddf1d8474d2c8d36923c3fa