Hylki (formerly known as Vireo) is a fast, modern, privacy-first email client designed specifically for the Linux desktop. Released as free and open-source software under the GNU AGPLv3 license, it delivers a feature-rich email experience while adhering to GNOME-native design principles.

Key features and capabilities of Hylki include:

• Native GNOME Stack & System Integration: Built in Rust using GTK4 and libadwaita for instant startup and fluid performance. It integrates directly with GNOME Online Accounts (enabling token-based OAuth sign-in for Gmail and Outlook/Microsoft 365), GNOME Contacts for autocompletion, GNOME Files, and system keyrings like GNOME Keyring and KWallet.

• Inbox & Organization Tools: Features a modern three-pane layout with a unified inbox combining all accounts, grouped message threading, server-synced colored tags (stored as IMAP keywords), and automated sorting rules.

• Privacy & Security by Default: Operates with zero telemetry or tracking, blocks tracking pixels and remote images by default, stores credentials securely in the OS secret service, and supports end-to-end OpenPGP email encryption and signing via GnuPG.

• Real-Time Delivery & Advanced Mail Tools: Supports real-time IMAP IDLE push notifications, Proton Bridge connections, scheduled "Send later" mail delivery, a visual attachment grid with full previews, and cloud attachment link sharing (via Nextcloud, ownCloud, OneDrive, Dropbox, and Seafile).

• Local & AI-Free Runtime: While parts of the codebase were developed with AI assistance (Claude), the application itself contains zero runtime AI features or service calls, ensuring your email data remains completely local to your machine.