The Windows Store app is no more! New computers no longer have it pre-installed. If you have it installed you can continue to use it. Microsoft is looking into creating a migration utility, as installing Click-to-run version will delete all settings, Outlook profiles - basically everything stored in the registry and AppData\Local and AppData\Roaming paths. If you use an IMAP account with 'This Computer only" folders, you need to export the contents of those folders before you switch to Click-to-run. Instructions to export the Outlook profile from the registry are here: Outlook Windows Store Registry

The Microsoft App Store version of Office (codenamed Centennial) changes a few things in Outlook.

Known issues: Addins, including iCloud, may not work. iCalendar files (.ics) may not open in Outlook, and Signatures and Stationery buttons doesn't work.

As of Office version 16.0.9027.1000 and higher, installing the click-to-run version will uninstall the store apps as part of the installation process. If you prefer, you can uninstall the store version yourself before installing Office.

How do you know what version is installed? Look on the File, Office Account dialog. The About Outlook dialog will say Windows Store:

In addition, you won't have a Control Panel, Mail applet to manage profiles. To access the Manage profiles dialog, start Outlook using the /manageprofiles switch.

To open outlook with the /manageprofiles switch:

1. Close Outlook.
2. Right-click on the Start button and choose Run or press Windows key + R to open the Run command.
3. Type or paste the following into the Open field and press Enter or click OK to restart Outlook. (There is a space before /.)
   

    outlook.exe /manageprofiles

If you need to switch profiles, you can do so from Outlook's File, Account Settings menu, selecting either Change Profile or Manage Profiles.

If Outlook won't start and you want to try creating a new profile, use the /profiles startup switch.

1. Press Windows key + R to open the Run command.
2. Type or paste outlook.exe /profiles in the Open field and press Enter on your keyboard.
   
3. Click Options to expand the Choose Profile dialog
   
4. Click Properties to open the Accounts settings dialog and edit the the profile.
5. Choose New if you then follow to wizard to create the profile and add accounts to it.
   

Data files for Microsoft Exchange (including Outlook.com) and IMAP accounts are now stored at C:\Users\%username%\AppData\Local\Packages\Microsoft.Office.Desktop_8wekyb3d8bbwe\LocalCache\Local\Microsoft\Outlook_AppX

Use this shortcut to access the data files or right click on the mailbox name and choose Open File Location

%localappdata%\Packages

Everything normally stored in the %localappdata%\microsoft and %appdata%\microsoft may be in the package path.

Frankly, using the package path as the default location is a very bad, horrible idea - those folders are deleted if you remove the app store version and switch to Click to run.

 
Signatures are stored at C:\Users\%username%\AppData\Local\Packages\Microsoft.Office.Desktop_8wekyb3d8bbwe\LocalCache\Roaming\Microsoft\Signatures

Outlook uses pointers to make it appear the signature files are in the usual signature folder (at %appdata%\Microsoft\Signatures). If you copy signature files to the usual folder, Outlook will include them in the list of available signatures. When you assign a signature to an account (or change the signature when composing a message), Outlook copies it into the Signature folder in the Appx path (above).

If you use the registry key to move the signature folder, Outlook creates that folder under the appx folders and copes the assigned signatures to the folder.

Templates are shown in the template selection dialog as being in the standard template folder: C:\Users\%username%\AppData\Roaming\Microsoft\Templates but they are not actually there; you'll find the templates at C:\Users\%username%\AppData\Local\Packages\Microsoft.Office.Desktop_8wekyb3d8bbwe\LocalCache\Roaming\Microsoft\Templates.

The profile is stored in the registry as virtual keys at

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Profiles_AppX

C:\Program Files\WindowsApps\Microsoft.Office.Desktop.Outlook_16010.8827.2159.0_x86__8wekyb3d8bbwe\Office16\

Addin Support

If you are using Windows 10S, you'll be limited to addins in the Office store. Users with other Windows 10 versions will be able to install COM addins, but they may not work.

Uninstall the Store version

You can uninstall the store version then install the click to run version from office.com. While it is not always necessary, I recommend rebooting after uninstalling the store version before installing click to run from office.com (or any other Office suite).

If you use an IMAP account and have entries in Calendar, Contacts, or Tasks folders labeled 'This computer only', export the contents to a pst or csv file before uninstalling this version of Office. Your profile will be deleted. You may also want to copy signatures to the "normal" default location.

Both versions are linked to the subscription associated with your Microsoft account.

1. Open Settings, Find Apps & features.
2. Click on the Office Desktop App and select Uninstall
   
3. A second small Uninstall dialog will open, for you to confirm that you want to uninstall it.
   
4. When it is complete, you should reboot before installing a different Office version.

If you prefer using PowerShell, follow these steps:
Open PowerShell in run as admin mode then paste:

Get-AppxProvisionedPackage -Online | where-object {$_.packagename –like "*Outlook*"} | Remove-AppxProvisionedPackage -Online

Then:

Get-AppxPackage "*Outlook*" | Remove-AppxPackage

Close the PowerShell window and open it without using run as admin. Run this command:

Get-AppxPackage "*Outlook*" | Remove-AppxPackage