Calendar sharing error in Microsoft 365

Error

When sharing calendars with others in Office 365, this message may appear:  "Error: This recipient's organization is not set up for secure sharing."

Resolution

Most often this is caused by the customer not searching for the recipient using the Global Address List (GAL). To make sure they are searching in the GAL, do one of the following:

Clear Auto-complete

1. Right-click the calendar to share.
2. Select Share  >  Share Calendar.
3. Start typing the name or eID of the intended recipient.
4. When an address is presented by auto complete in Outlook on the web or Outlook on the desktop, click the X to the right to remove the stored account information.
5. Manually type in the correct eID/email for the Shared calendar.
6. Send the calendar invite.

OR

Select from Global Address List

1. Right-click the calendar to share.
2. Select Share  >  Share Calendar.
3. Click To…
4. In the Address Book drop down, select Global Address List.
5. Search for the name of the intended recipient.
6. Double-click the name to add it in the To -> field.
7. Click OK.
8. Send the calendar invite.