Troubleshooting Tip: Unable to add a FortiMail calendar to Microsoft Outlook
Description
This article describes why a FortiMail calendar cannot be added or synchronized in Microsoft Outlook, and explains how to subscribe to the calendar correctly using the iCal (ICS) URL.
Scope
FortiMail (all versions that support Calendar Publishing).
Microsoft Outlook (Windows desktop).
Solution
FortiMail changed the mechanism for calendar subscription. WebDAV now publishes only, while the iCal URL handles subscription:
WebDAV – Publish only.
iCal URL – Subscribe.
Microsoft Outlook desktop supports iCal subscriptions, but Outlook mobile apps do not. Subscribing through WebDAV produces errors such as a missing DirectoryIndex or a failure to retrieve the calendar.
Solution
Verify that the FortiMail calendar is published.
Log in to the FortiMail GUI.
Navigate to: Calendar -> Public Calendar.
Confirm the calendar is published and the iCal URL is visible.
Obtain the correct iCal URL.
In FortiMail, open the calendar Properties.
Locate the field labeled iCal URL.
Copy the full URL (ending in .ics).
Add the iCal calendar in Microsoft Outlook (Windows desktop).
Open Outlook.
Go to: File -> Account Settings -> Account Settings
Select the Internet Calendars tab.
Select New.
Paste the iCal URL from FortiMail.
Complete the wizard and allow Outlook to synchronize.
(Optional) Reset the Outlook calendar settings.
If synchronization still fails, do the following:
Go to: File -> Options -> Advanced.
Under Send/Receive, select: Send/Receive…
Reset or recreate the calendar subscription.
Important notes:
WebDAV cannot subscribe to FortiMail calendars. It supports publishing a calendar only. Use the iCal URL for all subscription scenarios.
Outlook for Android and iOS does not support iCal, WebDAV, or CalDAV. These mobile apps support calendars only from Exchange / Microsoft 365, Outlook.com, and Gmail (via Google APIs).
To access FortiMail calendars on mobile devices, use one of the following:
A third-party calendar app that supports iCal subscriptions, or
A device-native calendar app that allows adding ICS URLs (varies by OS).
