Hi Franck,

This is a known behavior due to how Outlook handles calendar synchronization.

When participants are added, Odoo treats the event as a meeting, and Outlook expects valid email addresses for attendees. If none of the participants have valid emails, Outlook cannot process it correctly and fails instead of creating a simple appointment.

In standard Odoo, there is no direct configuration to handle this scenario differently. As a workaround, you may consider:

• Avoiding adding participants without emails for events that need Outlook sync, or

• Keeping such contacts linked in another way (e.g., notes or CRM activities) instead of as calendar attendees

Handling this automatically (e.g., converting such events into appointments) would require customization.

Hope this works for you! Feel free to reach out for further discussion.

Regards,

Zehntech Technologies Inc.

santosh.sekwadia@zehntech.com