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KontactBusyContacts
Free

Free and open source, developed by the KDE community.

 Paid

Costs $49.99 USD with a 14-day free trial; also available through Setapp.

Linux macOS
  • Mail, calendar, contacts and feeds in one window
  • Works offline with your data
  • Direct sync with iCloud, Google, Exchange and CardDAV
  • Tags, smart filters and per-contact activity history
  • Best suited to the KDE Plasma desktop
  • Large suite with many settings to learn
  • macOS only
  • One-time paid purchase after the trial
Downloadable app Downloadable app
Open source Closed source
License not stated License not stated
No account needed No account needed
Works offline Not stated if it works offline

Checked September 24, 2026

Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.