New storage location. Previously you'd find many of Outlook's components (the database and message attachments, for example) in the Microsoft User Data folder inside your Documents folder. All these elements have now shifted to a place deep within the Library folder inside your user folder. Specifically, you'll find them here:
~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile
A few missing features
Whether to make the shipping deadline or simply because Microsoft felt the features were no longer necessary, there are some things you can no longer do with Outlook.
Import/export business. You'll find no Export command in the File menu. This means that you can't export contacts in a tab-delimited list nor can you export a Mac Data File of your Outlook mail, tasks, contacts, notes, and calendars. You can, however, still drag a mailbox from Outlook to the desktop to turn it into a .mbox archive, which can be imported by most email clients. Importing data is also now more limited. You can import .olm or PST archives but you can't import old Entourage archives or pull in contacts within text files.
Automation more limited. Automator actions are entirely gone and a dedicated AppleScript menu is missing. However, Outlook is still scriptable. You simply need to switch on the general AppleScript menu within AppleScript Editor and then move your Outlook AppleScripts into the folder dedicated to it. (This should come as a relief to those using SpamSieve, which relies on AppleScript.)
So long to Sync Services. Sync Services, which could be problematic when sharing information between Outlook and Apple's Mail, Contacts, and Calendar has been removed. Apple similarly abandoned Sync Services for everything but syncing contact and calendar data between a Mac and iOS device in OS X 10.9. This won't change much for most Outlook users who either managed all their email, calendars, and events within it or were happy to delegate Outlook to their email and otherwise use Apple's Contacts and Calendar apps.
Outlook 2015 is not a release packed with new features. It's already a very capable email client. Rather, it's an update that hopefully makes it faster and more reliable as well as brings it into line with other Microsoft efforts including Outlook for Windows and Office 365. If you're an Office 365 subscriber it's worth your while to give it a try.
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