Fastmail

Build me a focused email clients and hosted mail workflow for the personal core of Fastmail. Requirements:

- Use Tauri 2, React, TypeScript, SQLite, IMAP, SMTP, and OAuth where available. Model mail accounts, message IDs, threads, folders, and pending actions; keep stable source IDs and timestamps.
- Paid product context: Build a clean client for an existing mailbox without running public mail infrastructure. Build only this DIY scope: Connect an existing mailbox, index messages locally, provide a fast focused inbox, and send through the account's normal SMTP service without running public mail infrastructure.
- Support one IMAP and SMTP account with credentials stored only in the OS keychain.
- Implement standards-based threading, folders, labels, archive, snooze, drafts, and search.
- Render HTML email in a locked-down sandbox and block remote images by default. Send multipart messages with attachments and preserve a local copy of every draft. Add export, local cache reset, account reconnect, diagnostics, and safe logging.
- Use a desktop window with source import, a work list, and result export. Required input or access: existing IMAP and SMTP mailbox; OAuth client credentials where required. Keep credentials in .env.
- Recovery: Record delivery failures and retries by message ID; never duplicate a send after restart.
- Acceptance: with one labelled sample, show the input, saved intermediate state, and exported result; verify this invariant: A reconnect must not duplicate mail; after an ambiguous send response, retain pending status until the provider confirms it.
- Out of scope: mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support; mail hosting and deliverability. Keep this a personal, inspectable workflow.
- Include a README with setup, a sample input, required keys or permissions, data location, and the supported scope.

# AGENTS.md — Build guide for Fastmail

## Project scope
Connect an existing mailbox, index messages locally, provide a fast focused inbox, and send through the account's normal SMTP service without running public mail infrastructure.

Catalogue verdict: no. A consolation build is possible, but the paid product's decisive value sits outside a solo rebuild. For Fastmail, build a clean client for an existing mailbox without running public mail infrastructure. The hard boundary is mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support, plus mail infrastructure, integrations, and client polish.
Use the implementation prompt below to define the deliverable. Complete each phase's acceptance checks before extending the scope.

## Working agreement
- Inspect the repository and its existing instructions before choosing paths, dependencies or commands. Keep one coherent stack and explain changes to the proposed architecture.
- Plan a vertical slice that accepts a real input and produces the useful output described below. Persist only the state the prompt calls for; respect memory-only and upstream-managed workflows. Use fixtures only when they are clearly labelled.
- After scaffolding, document the actual install, development, check and build commands in README and keep them synchronized with the package or project manifest. Do not report commands as successful unless they ran.
- Work in small steps. At handoff, list implemented flows, checks actually performed, remaining blockers, and any credentials or provider setup the owner must supply.
- Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization.

## Prerequisites
- existing IMAP and SMTP mailbox
- OAuth client credentials where required
- desktop keychain access
- local disk space

## Stack and architecture
- Use Tauri 2, React, TypeScript, SQLite, IMAP, SMTP, and OAuth where available.
- Model mail accounts, message IDs, threads, folders, and pending actions; keep stable source IDs and timestamps.
- Interface for this email clients and hosted mail workflow: a desktop window with source import, a work list, and result export.

## Security and data integrity
- Record delivery failures and retries by message ID; never duplicate a send after restart.
- Keep API keys and OAuth secrets in .env; redact them from logs, generated files, and error responses.
- State the practical limit: mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support.

## Agent implementation rules
- Project rule, data: Model mail accounts, message IDs, threads, folders, and pending actions; keep stable source IDs and timestamps.
- Project rule, behavior: Support one IMAP and SMTP account with credentials stored only in the OS keychain.
- Project rule, recovery: Record delivery failures and retries by message ID; never duplicate a send after restart.

## Optional agent skills and references
No installable skill is listed for this guide; use the project rules and the stack documentation.

Read the linked SKILL.md and its dependencies before adding a skill. Select only the skills matching this project's runtime and task; their documentation does not supply API access, credentials or approval to perform external actions. Pin the reviewed revision where the tool supports it. Follow the chosen agent's documented project-level installation mechanism.

## Distribution ideas
These are optional planning notes. Obtain the owner's approval before publishing or contacting anyone.
- Demonstrate this email clients and hosted mail operation with sample or user-owned data: Support one IMAP and SMTP account with credentials stored only in the OS keychain.
- Show a concrete result or export: Add export, local cache reset, account reconnect, diagnostics, and safe logging.
- State the practical limit: mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support.

## Engineering roadmap
1. Phase 1, architecture and data: Use Tauri 2, React, TypeScript, SQLite, IMAP, SMTP, and OAuth where available. Model mail accounts, message IDs, threads, folders, and pending actions; keep stable source IDs and timestamps.
2. Phase 2, implement: Support one IMAP and SMTP account with credentials stored only in the OS keychain.
3. Phase 3, implement: Implement standards-based threading, folders, labels, archive, snooze, drafts, and search.
4. Phase 4, review and output: Render HTML email in a locked-down sandbox and block remote images by default. Add export, local cache reset, account reconnect, diagnostics, and safe logging.
5. Phase 5, recovery and acceptance: Record delivery failures and retries by message ID; never duplicate a send after restart. Verify this invariant with a saved fixture: A reconnect must not duplicate mail; after an ambiguous send response, retain pending status until the provider confirms it. State the practical limit: mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support.

## Paid-product capabilities outside this build
- mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support
- mail hosting and deliverability
- push on every platform
- advanced team collaboration
- provider-specific AI and search

## Implementation prompt
Build me a focused email clients and hosted mail workflow for the personal core of Fastmail. Requirements:

- Use Tauri 2, React, TypeScript, SQLite, IMAP, SMTP, and OAuth where available. Model mail accounts, message IDs, threads, folders, and pending actions; keep stable source IDs and timestamps.
- Paid product context: Build a clean client for an existing mailbox without running public mail infrastructure. Build only this DIY scope: Connect an existing mailbox, index messages locally, provide a fast focused inbox, and send through the account's normal SMTP service without running public mail infrastructure.
- Support one IMAP and SMTP account with credentials stored only in the OS keychain.
- Implement standards-based threading, folders, labels, archive, snooze, drafts, and search.
- Render HTML email in a locked-down sandbox and block remote images by default. Send multipart messages with attachments and preserve a local copy of every draft. Add export, local cache reset, account reconnect, diagnostics, and safe logging.
- Use a desktop window with source import, a work list, and result export. Required input or access: existing IMAP and SMTP mailbox; OAuth client credentials where required. Keep credentials in .env.
- Recovery: Record delivery failures and retries by message ID; never duplicate a send after restart.
- Acceptance: with one labelled sample, show the input, saved intermediate state, and exported result; verify this invariant: A reconnect must not duplicate mail; after an ambiguous send response, retain pending status until the provider confirms it.
- Out of scope: mail hosting, spam filtering, domains, calendars, contacts, deliverability, and support; mail hosting and deliverability. Keep this a personal, inspectable workflow.
- Include a README with setup, a sample input, required keys or permissions, data location, and the supported scope.

## Completion evidence
Demonstrate the prompt's acceptance scenarios against the scoped workflow. Include setup from a clean checkout and failure recovery. Check persistence across restart and export/restore only for the state the prompt says to store; for memory-only tools, confirm that temporary content is discarded as specified. Record actual results and remaining limitations. A detailed plan alone does not establish a working replacement.