Technology
Under the hood.
For admins, developers and anyone who wants the details: what Neruna talks to, where it keeps data and how it's built.
- Platforms
- Windows 10 and 11 (64-bit) as a beta · Linux and macOS from source
- Protocols
- IMAP · SMTP · CalDAV · CardDAV · ICS/webcal · Microsoft Graph
- Formats
- MIME · iCalendar · vCard · S/MIME
- Storage
- Local SQLite database as an offline copy
- Passwords
- In the system keychain – Windows Credential Manager, macOS Keychain, Secret Service on Linux; without one, encrypted in the data folder. Never in the database, never in logs.
- Updates
- In the background, installed at the next start
- Languages
- German, English, French, Italian
- Licence
- Mozilla Public License 2.0
01 Architecture
Swappable providers instead of hard-wired protocols.
The interface only talks to three areas: mail, calendar and contacts. Behind them sit providers – one per protocol. Only standard formats flow between providers and storage: MIME, iCalendar and vCard.
That's how Microsoft 365 was added without changing the interface or storage – and how more providers will follow.
02 Protocols & standards
| Area | Standard | Notes |
|---|---|---|
| IMAP4rev1, SMTP (Submission) | New mail instantly via IMAP IDLE; folder subscriptions on the server; server-side search | |
| Calendar | CalDAV, iCalendar, ICS/webcal | Invitations and replies (iTIP); subscriptions read-only |
| Contacts | CardDAV, vCard 3.0/4.0 | Groups in the common CardDAV format, contact photos |
| Microsoft 365 · Outlook.com | Microsoft Graph, OAuth 2.0 (PKCE) | Sign-in in the browser; Neruna never sees the password. Mail, calendar, contacts |
| Setup | Autoconfig, .well-known | Server settings from the provider or a public provider database; editable by hand |
| S/MIME | CMS, X.509 | Automatic signing and encryption; algorithms selectable |
03 Sync
Fast, frugal, readable offline.
- Inbox instantly via IMAP IDLE; without IDLE every 2 minutes
- All other folders, calendars and contacts every 5 minutes – changes only
- Microsoft 365 via delta queries, the last 90 days at first, older mail on demand
- Changes on both sides are guarded by versions (ETags)
04 Building blocks
Solid, open libraries.
- .NET 10 runtime, cross-platform
- Avalonia 12 interface for Windows, Linux and macOS
- MailKit · MimeKit IMAP, SMTP, MIME, S/MIME
- Ical.Net iCalendar, recurrence, time zones
- EF Core · SQLite local offline copy
- WebView2 · WebKitGTK formatted writing (Windows or Linux)
- Velopack installer and automatic updates
05 Neruna Cloud · Control
The portal knows configuration. No content.
Neruna Cloud runs in Switzerland (PHP/Laravel, MariaDB). Neruna Control will be the same software on your own server, via Docker – in development.
- Device keys Every device has its own key pair (ECDSA P-256); the private part never leaves the computer. Sign-in with short-lived tokens.
- Zero knowledge for secrets Certificate keys and account passwords are encrypted per device (ECDH P-256, HKDF, AES-GCM). The server only stores what it can't read.
- Vault Personal backups with a key derived from your vault password (Argon2id) and AES-GCM.
- Signed settings Account server settings are signed – nobody can redirect passwords to another server.