Synapse
Synapse: A low-cost Windows client for secure, local-first email management. Ranked #35 of 142 in Email Clients by our editors (5.9/10); pricing: Paid; best for windows users wanting secure offline email.
At a glance
- Editor score5.9 / 10
- PricingPaid
- Best forWindows users wanting secure offline email
- Free planNo
- Paid from€4.99 one-time
- App coverageDesktop
- Facts checked20 Sep 2026
Where it wins
- €4.99 one-time purchase includes lifetime access and future updates
- Offline cache, local AI, semantic search, and encrypted credential storage
- Unified inbox with Gmail, IMAP/SMTP, calendar, task, and reminder support
Where it doesn't
- Available only as a Windows desktop application
- Requires a paid €4.99 one-time purchase
- The product is described as being in active development
Our verdict on Synapse
Synapse is a Windows desktop email client for people who want local processing, offline access, and one-time pricing. It supports Gmail through the Gmail REST API alongside generic IMAP/SMTP accounts, combining messages in a unified inbox with threaded conversation views. The product is aimed at Windows users who want email stored and processed locally rather than synchronized through a centralized service, while still connecting email with everyday productivity tools.
Its strongest distinction is the combination of offline-first storage and local intelligence. Synapse uses a SQLite mail cache, IMAP IDLE push synchronization, BM25 and semantic email search, and on-device AI assistance using a local model. Credentials are stored in an encrypted SQLCipher vault bound to TPM 2.0. These features make the client a considered choice for users who prioritize local handling of email and want search and AI assistance without relying on a remote processing workflow. One-click mailing-list unsubscribe and support for Italian PEC certified email add practical scope for specific email needs.
The €4.99 one-time Synapse plan includes lifetime access, all future updates, and no subscription, according to the published pricing details. Plugins for Asana, ClickUp, Google Calendar, and reminders extend the application beyond inbox management. The main trade-off is platform coverage: Synapse is available as a Windows desktop application, so it is not a fit for users who need a broader device ecosystem. The vendor describes the product as in active development and invites users to join a launch waitlist. Choose Synapse for a low-cost, local-first Windows email workflow; choose an alternative if cross-platform access is essential.
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Synapse pricing
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Synapse fact sheet
| Free plan | No |
|---|---|
| Paid from | €4.99 one-time |
| App coverage | Desktop |
| Account limit | Not verified |
| Unified inbox | Yes |
| Offline access | Yes |
| Scheduled sending | Not verified |
| Calendar tools | Yes |
| Deployment | Desktop |
| Platforms | Windows |
| Compliance & security | GDPR |
| Support | |
| Built for | Solo, Small business, Mid-market (editorial estimate) |
| Integrations | 4 integrations: Asana, ClickUp, Google Calendar, Reminders |
| Pricing | Paid (source) |
| Website | synapsemail.app |
| Facts checked | 20 Sep 2026 |
Synapse integrations
Synapse lists 4 integrations on its own site.
- Asana
- ClickUp
- Google Calendar
- Reminders
Alternatives to Synapse
- Mozilla ThunderbirdA capable free client for multi-account email, offline access, and desktop productivity tools.9.4
- Zoho MailA flexible hosted email service with free access, migration tools, and Zoho collaboration options.9.2
- Apple MailA capable Apple-focused email client with unified inboxes, scheduling, privacy controls, and AI assistance.9.1
See all Synapse alternatives →
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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