Microsoft Outlook: The Best Open-Source Alternatives

Microsoft Outlook positions itself as an email and calendar application for managing appointments, tasks, and contacts.

The directory lists Microsoft Outlook in the «Calendar» category.

Here you can find open-source alternatives, and separately marked source-available alternatives, to «Microsoft Outlook» (external link) in the category «Calendar».

In the Category «Calendar»

ERPNext

ERPNext combines accounting, quotes, invoices, and time tracking with subscription and contract management in one web application.

  • Accounting
  • Appointment Scheduling
  • Calendar
  • Contracts
  • CRM
  • ERP
  • Invoicing
  • Project Time Tracking

Nextcloud

Nextcloud stores and shares files and syncs them across devices. Teams access them through the browser, desktop, and mobile devices.

  • Calendar
  • File Sync and Sharing

Odoo Community

Odoo Community brings together sales, purchasing, inventory, invoicing, calendar, and time tracking in a modular business suite.

  • Calendar
  • CRM
  • Employee Time Tracking
  • ERP
  • Invoicing
  • Project Time Tracking

SOGo

SOGo combines calendars, contacts and webmail to help teams organize appointments and communication.

  • Calendar

XWiki

XWiki manages company knowledge and public wiki pages with a visual editor, search, versioning, and access rights. An optional paid app adds team calendars.

  • Calendar
  • CMS
  • Knowledge Bases