# PaperPlane

> A Windows desktop mail client that draws every conversation as a tree.
> Who replied to whom, where the thread branched, where each branch stopped —
> across every connected account.

## What it is

PaperPlane is a native Windows (WPF, .NET) mail client. Its distinguishing feature is
the conversation tree: instead of flattening a thread into a list, PaperPlane
reconstructs the reply structure from mail headers and draws it as a real tree, with
received and sent marked on each node.

Because one conversation is rarely one thread, the tree's scope can be widened from
"this conversation" to "this subject", "this person", "this host" or "this whole
domain" — so a discussion that moved to a new subject line, or to a different address,
still reads as a single conversation.

It is made by dhq-boiler, an individual developer in Japan, who also builds
boiler's Graphics, STREAM DIRECTOR and JidoDebugger.

## Key facts

- Platform: Windows 10 and Windows 11 only. No macOS or Linux build exists or is promised.
- Price: 9.99 USD / month, or 99 USD / year (two months cheaper). 14-day free trial
  with no card required on either plan.
- Billing: Paddle.com Market Ltd acts as merchant of record; VAT and sales tax are
  calculated and included at checkout.
- Refunds: full refund within 30 days of a charge, no justification required.
- Privacy: mail is fetched by the desktop app directly from the user's provider and
  cached in a local SQLite database. No server operated by PaperPlane sits in the path
  of the user's mail. Credentials are sealed with Windows DPAPI.

## Features

- Conversation tree drawing replies, forwards and branches, with received/sent per node.
- Scope widening: this conversation / this subject / this person / this host / this domain.
- Tree reconstruction from Message-Id, In-Reply-To and References headers, falling back
  to subject and participant matching only when a client has stripped those headers.
- Bulk and no-reply mail detection, so a mass mailing does not collapse into one fake
  thread that buries real conversations.
- Accounts: Gmail and Microsoft 365 via OAuth; iCloud and Yahoo via app passwords;
  anything else over IMAP and SMTP. Unified inbox, and trees span accounts.
- Local SQLite cache, offline reading, search against the local disk.
- Remote image blocking, plain-text forcing, dark and light themes, English and
  Japanese UI.

## Pages

- Home: https://paperplane.dhq-boiler.dev/
- Privacy policy: https://paperplane.dhq-boiler.dev/privacy
- Terms of service: https://paperplane.dhq-boiler.dev/terms
- Refund policy: https://paperplane.dhq-boiler.dev/refund
- Contact: https://paperplane.dhq-boiler.dev/contact

## Contact

support.paperplane@dhq-boiler.dev