Outlook alternative
Keep your Outlook account.
Ditch the M365 subscription.
Synapse connects to your existing Microsoft account via OAuth, with no email migration, no PST files, no hassle. You keep all your mail where it is; Synapse just gives you a faster, more private way to read it. One payment of €4.99 vs $10/mo for M365.
No account required · Payment via Gumroad
The 5-year cost
Synapse
€4.99
Total. Forever.
Microsoft 365 Personal
$600
~$9.99/mo × 60 months
No migration required
Add your Microsoft account to Synapse with a two-click OAuth flow via your system browser. Synapse authenticates with Microsoft's servers, then syncs your mail directly to a local SQLite cache. Your mail stays in your Exchange or Outlook.com mailbox. You can keep using the Outlook web app or mobile app alongside Synapse with no conflicts.
No Microsoft telemetry
Microsoft 365 and the Outlook app collect diagnostic data, usage analytics, and content signals that feed into their advertising and AI products. Synapse sends nothing: 0 telemetry, 0 analytics. The only network connections are your IMAP/SMTP traffic to Microsoft's servers and the optional update check at startup.
AI without Copilot
Microsoft's Copilot in Outlook sends your email content to Azure OpenAI. Synapse runs AI locally on your GPU via Vulkan (Qwen3.5-4B), entirely offline after a one-time ~2.5 GB download from Settings → AI. No Azure. No Copilot subscription. No prompts leaving your machine.
Faster search, offline
Outlook's local search relies on Windows Search indexing, which is slow and often broken. Synapse maintains its own FTS5 full-text index and semantic embedding index, both queried in milliseconds. Search works fully offline, even if your Exchange server is unreachable.
Lifetime access · All future updates included
Email done right
- Gmail REST API + IMAP IDLE push for all other providers, no polling
- Thread view with expandable conversations and newest-first toggle
- Bulk actions: move, delete, archive, mark read with keyboard support
- One-click unsubscribe from any mailing list
- Open .eml attachments inline without leaving your inbox
- Italian PEC certified email (S/MIME auto-extracted)
- OAuth2 for Google and Microsoft, password never stored
Search that actually works
- Gmail-style query DSL: from:, subject:, is:unread, has:attachment and more
- BM25 full-text + 768-dim multilingual semantic search, 100+ languages
- Smart reranker: keyword score, semantic similarity, recency, personal history
- Search inside attachments and nested .eml files
- Saved searches, history, and contact autocomplete typeahead
AI without the cloud
- On-device AI assistant (Qwen3.5-4B, Vulkan GPU)
- Local model: 0 bytes to OpenAI. Or BYOK your own key.
- Grammar-constrained plugin output: structured JSON, no hallucinated fields
- Auto low-memory mode on machines with 16 GB RAM or less
Privacy you can verify
- TPM-sealed AES-256 credential vault
- Offline-first SQLite, all data stays on your machine
- 0 telemetry, 0 analytics, 0 cloud relay
What else you get
- Asana · ClickUp · Calendar · Reminders plugins
- 28 themes across light, dark, half-dark, and aurora variants
- Gmail-style and Mailbird-style keyboard shortcut presets
- Multi-language spellcheck in compose
- Built-in address book
- Automatic Ed25519-signed updates, no manual downloads