Free-busy does not return the expected results

When calling free-busy, the endpoint returns an empty array or is missing busy slots.

If passing emails then the endpoint only works with

  • Microsoft (primary calendar)
  • Gmail (primary calendar)

Always use email addresses where possible as this will return the free-busy directly the provider. There is a limitation on how far in the future you can return free-busy within your application limit this to the shortest period which is Microsoft 62 days.


If emails does not work a backup method would be using passing calendar_id's which also works with:

  • iCloud
  • Virtual calendars
  • Additional calendars


To resolve issue with emails not return free-busy please try the following:

  1. Have the customer run EWS test, does the (Getting user availability and confirming results against expected values) part of the test pass?
  2. If it is failing then please pass the following information to the mail administrator:
    1. How Free Busy works
    2. Potential fix




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