# Inbox Classic > Inbox Classic is a free, open source (MIT) email client for Windows, Mac and Linux with the classic three-pane layout: folders on the left, the message list on top and the reading pane below. It works with Outlook.com, Microsoft 365, Gmail and any IMAP and SMTP account. It has no ads, no analytics, no sign-up and no account with its makers. It is made by Postal Systems, the makers of Nodemailer and EmailEngine. On Windows it looks like a classic Windows mail program; on the Mac it is a native AppKit app and on Linux a native GTK 4 app, all with the same layout and features. IMAP, SMTP and MIME run in one shared Rust core, which also sanitizes every message before it is shown. ## Download - [Windows installer](https://github.com/postalsys/inbox-classic/releases/latest/download/InboxClassic-Setup.exe): Windows 10 and 11, installs per user without admin rights - [Mac disk image](https://github.com/postalsys/inbox-classic/releases/latest/download/InboxClassic.dmg): macOS 26 or newer on Apple silicon, signed and notarized, updates itself - [Linux .deb for x86-64](https://github.com/postalsys/inbox-classic/releases/latest/download/InboxClassic-amd64.deb): Ubuntu 26.04 or newer - [Linux .deb for ARM64](https://github.com/postalsys/inbox-classic/releases/latest/download/InboxClassic-arm64.deb): Ubuntu 26.04 or newer - [Arch Linux and Omarchy package for x86-64](https://github.com/postalsys/inbox-classic/releases/latest/download/InboxClassic-x86_64.pkg.tar.zst) and [for ARM](https://github.com/postalsys/inbox-classic/releases/latest/download/InboxClassic-aarch64.pkg.tar.zst): install with `sudo pacman -U` on the downloaded file - [Linux apt repository](https://inboxclassic.com/#linux-apt): package `inbox-classic` for amd64 and arm64, signed with the Postal Systems release key; add it with `sudo wget -qO /etc/apt/sources.list.d/inboxclassic.sources https://apt.inboxclassic.com/inboxclassic.sources`, then `sudo apt update && sudo apt install inbox-classic`. Updates come with the system updates. Linux packages newer than 0.9.0 add the repository by themselves when installed - [Release notes](https://github.com/postalsys/inbox-classic/releases): what is new in each version ## Features - Accounts: Outlook.com and Microsoft 365 sign in on Microsoft's own page (OAuth). Gmail works with a Google app password or a Google sign-in app of the user's own. For any other address the IMAP and SMTP servers are found automatically. Several accounts share one folder tree, each with a short name of its own (Gmail, Work) that the folder list shows. - Search: every folder at once, as you type, by subject, people, attachment names and text, with Gmail's search words (`from:`, `is:unread`, `has:attachment`). The search runs locally and works offline. - New mail: arrives right away (IMAP IDLE), with a notification and a count on the taskbar or the Dock, even while the window is closed. - Reading: mail is kept on the computer too, so it opens instantly and works offline. Long quoted reply histories fold away. All Inboxes shows the Inbox of every account in one list, with a row for each account's Inbox under it. Bounces are explained in plain words: for each address that failed or was delayed, what went wrong and what to do. A sign-in or verification code is shown in a card above the message with a Copy button, only when the provider confirms the site it is for signed the message; an option shows it in the new mail notification too. - Languages: English, German, Estonian, French and Spanish (the windows, the menus, the help and the Windows installer). It follows the system language, or the user picks one in the settings. - Writing: formatted or plain text, a signature per account, address completion, drag and drop attachments, and an Outbox that sends when back online. - Organizing: select several messages to mark, flag, junk, move, delete, forward or save them at once, with Undo. Flags in the seven colours Apple Mail uses. Move and copy messages between accounts. One-click unsubscribe and a Junk button. - Files: drag messages out of the list to save them as .eml files, drag .eml files onto a folder to import them. - AI agents: the user's own AI agent (Claude, Cursor, any MCP client) can search, read, organize and draft mail through Inbox Classic's MCP server. Add `{"mcpServers": {"inbox-classic": {"command": "", "args": ["--mcp"]}}}` to the agent's settings (Tools > AI Agents > How to Connect an Agent shows the exact lines). The user approves each agent program and the accounts it may use; every message an agent wants to send needs the user's yes and waits 30 seconds in the Outbox. There is no AI in the app itself. - Privacy: remote pictures that track opens stay blocked until the user allows them, scripts in messages never run, and the app sends nothing to its makers. Passwords are kept in the system's own password store (Windows Credential Manager, the macOS keychain, GNOME Keyring). ## Links - [Homepage](https://inboxclassic.com/) - [Source code on GitHub](https://github.com/postalsys/inbox-classic): MIT license, issues and discussions - [Privacy policy](https://inboxclassic.com/privacy): no accounts, no telemetry and no cookies; the website counts visits with self-hosted Plausible - [Terms of service](https://inboxclassic.com/terms) ## Optional - [Postal Systems](https://postalsys.com/): the company behind Inbox Classic - [Nodemailer](https://nodemailer.com/) and [EmailEngine](https://emailengine.app/): other email software by the same makers