A: Outlook has supported iCal at increasing levels over the years. iCal is a calendar application developed by Apple for the Mac. iCal is also the format for sharing calendar information between incongruent applications. The specification for iCal is described in RFC5545 (replacing long-held RFC2445). iCal is implemented as specifically formatted text files with the .ics extension.

Learn more from, "Connect Microsoft Email Clients to Gmail" and "First impressions of Outlook 2013 Preview."

After Outlook 2000, you were able to import and export calendar content with .ics-formatted files. You can access Internet calendars that use the .ics format through Outlook as well, which can import the content. But if the content changes at the source, third-party utilities are still needed to maintain synchronization with external iCalendars. (Outlook 2010 also still supports the lesser used vCalendar format, belonging to Internet Mail Consortium, allowing import of .vcs files.)

iCal files for import can be full calendars or specific calendar items. Recipients can import them into their iCal-supporting calendar application. Synchronization still isn't possible with shared iCal calendars, however. Third-party solutions are available, including using Google Calendar as an intermediary.

Microsoft added Internet Calendar Subscriptions in Outlook 2007, and the feature remains available in Outlook 2010. You can subscribe to an Internet-based calendar simply by clicking Open Calendar, From Internet in the Manage Calendars section of the Ribbon when Calendar is selected in Outlook 2010. You need the Webcal URL address of the Internet calendar, such as the one Figure 1 shows. I’ve used a Funny Holidays example from iCalShare.com.

Figure 1: Entering a new Internet calendar subscription URL

The Advanced button exposes configuration settings for the Internet calendar, which Figure 2 shows. When you click OK, a new Calendar is created in Outlook for the added Internet calendar. The iCal provider includes a synchronization frequency in the .ics file.

Figure 2: Configuration settings for Internet calendars

Internet calendars in Outlook automatically create a new .pst file, aptly named Internet Calendar Subscriptions.pst, located in \Users\\AppData\Local\Microsoft\Outlook. If you have a corporate policy prohibiting .pst files, enforced through Group Policy perhaps, users won't be able to subscribe to Internet calendars. There's no workaround for the .pst requirement for Internet Calendar Subscriptions in Outlook.

Overall, Outlook supports the iCal standard with .ics files, but it falls short of being a fully synchronizable iCal client.