Question 1

Why €4.99 and not free, or $30/mo like Superhuman?

Accepted Answer

Free means the product is the business model, which means your data is. Subscription means you never actually own it. The price goes up, they pivot, you start over. €4.99 covers the infrastructure cost of distributing and updating the app, with enough left over to keep me motivated. You pay once and I stop asking you for money.

Question 2

Can I migrate from Superhuman, Spark, or Outlook?

Accepted Answer

Yes, and it takes about two minutes. Add your Google or Microsoft account via OAuth. Synapse connects directly to your provider. Your mail syncs from the server automatically; there's nothing to import or export. Your old client can keep running alongside Synapse while you settle in.

Question 3

What if you stop developing Synapse?

Accepted Answer

I built this because I needed it, so I have no plans to stop. The app runs entirely locally with no server to shut down, no licence server to expire, no cloud account to delete. It will keep working forever regardless of what I do.

Question 4

Is my email data sent to the cloud?

Accepted Answer

By default, no. Email syncs directly from your provider to a local SQLite database on your machine. No cloud relay. No telemetry. No analytics. The only outbound connection is your IMAP/SMTP traffic to your own email provider, exactly the same as any other email client. The one exception is AI: if you configure a BYOK cloud model in Settings, your prompts go to that provider. If you use the built-in local model, nothing leaves your machine.

Question 5

How are my passwords and tokens stored?

Accepted Answer

Every credential (OAuth tokens, IMAP/SMTP passwords, plugin API keys) is stored in a SQLCipher-encrypted database (AES-256-CBC, HMAC-SHA512). The key is derived from your master passphrase via Argon2id and then sealed by your hardware TPM 2.0. On subsequent launches the TPM unwraps it silently. No password prompt unless you move to a new machine.

Question 6

Does Synapse work on Mac or Linux?

Accepted Answer

Not at this time. Synapse is built Windows-first and uses Windows-specific APIs: TPM 2.0 via NCrypt/DPAPI for the credential vault and Vulkan for GPU inference. A cross-platform port is not on the current roadmap, though it may come later.

Question 7

What GPU do I need for local AI?

Accepted Answer

Any Vulkan-capable GPU: Intel, AMD, or NVIDIA. If your GPU is not Vulkan-capable, the AI assistant is unavailable, but all email, search, and sync features work normally. The AI assistant is optional and requires a one-time ~2.5 GB model download from Settings -> AI.

Question 8

How do I receive updates after purchase?

Accepted Answer

Synapse checks for new releases silently at startup. If one is available, a slim banner appears. Click "Install & Restart" and it applies in the background. All updates are signed with an Ed25519 key verified against the public key embedded in the app. No manual downloads, ever.

Question 9

Can I contribute a plugin?

Accepted Answer

Yes. Reach out at hello@synapsemail.app and we can discuss building it together.

Feature	Synapse	Superhuman	Spark Premium	Outlook 365
5-year cost	€4.99 total	~$1,800	~$480	~$500
Monthly price	Free forever after	$30/mo	$8/mo	$10/mo (M365)
Data stays on your machine	✓ Always	✗ Cloud sync required	✗ Readdle servers	✗ Microsoft servers
AI processing	On-device GPU	OpenAI API	Spark servers	Microsoft Copilot API
Search	Offline FTS5 + semantic	Cloud-indexed	Cloud-indexed	Exchange / cloud-indexed
Works offline	100%	Limited	Limited	Partial (cached)
Credential storage	TPM-sealed AES-256 vault	Vendor-managed	Vendor-managed	Microsoft account
Updates	Lifetime included	Included in $30/mo	Included in $8/mo	Included in M365

€4.99. That's the whole bill.

Stop renting your inbox.

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