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Original KB number: 2800895

We do not recommend that you change the default location of your Profile folder for Microsoft Outlook 2016 for Mac, or your Identity folder for Microsoft Outlook for Mac 2011 to an external hard disk or to a network. Additionally, using a mail identity or profile that is located on an external hard disk or on a network is not supported in either version of Outlook for Mac.

Items from an Exchange account are stored in the Outlook cache. If this cache becomes corrupted, it may cause synchronization problems with the Exchange server. To solve this problem, you can empty the cache in Outlook so that Outlook 2016 for Mac can download. Download and open the Outlook Reset Preferences tool. Click the Reset Now! This closes Outlook if it's open, and then resets the preferences to their default settings.

More information

Outlook 2016 for Mac caches your mail items in a profile in your home folder at the following location:

Reset Outlook For Mac

~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles

Outlook for Mac 2011 caches your mail items in an identity in your home folder at the following location:

~/Documents/Microsoft User Data/Office 2011 Identities

Like Microsoft Entourage for Mac 2008, Outlook 2016 for Mac and Outlook for Mac 2011 are intended to be purely locally cached mail clients. Changing the location or using a mail identity that is located on an external hard disk or a network is not supported.

Lately I’m having some sync issues with my mailbox. For instance, I see several new emails in my mailbox when I login to webmail which I don’t see in Outlook.

Also, it looks like the entire month of June has gone missing in Outlook but the emails are luckily still available on the server.

Support

Is there any way to get Outlook to sync or download these emails again?

Reset Outlook For Mac

Corruptions in the cache are rare (especially for Exchange based accounts) but can still happen under various circumstances like an unexpected shutdown or crash of your computer or Outlook.

In these cases, it might be best to reset the local cache of Outlook and let it rebuild. The process is fairly simple to perform but make sure you do some checks first.

Step 1: Verify that the messages still exist on the server

The first thing to check is whether all messages that you expect to be on the mail server (via webmail) are still there as well.

You don’t actually have to check each and every message. With sync issues you are usually missing emails in Outlook and not in webmail. However, you do want to pay a bit more attention to folders you recently moved emails into and your Sent Items folder.

If you are missing any emails on the server, either drag & drop them out of Outlook and into a folder in your Documents folder (via File Explorer) to save them as msg-file or export/copy them to a pst-file.

Reset Outlook For Mac

Both methods will allow you to restore these items to Outlook and/or the mail server later on.


Drag & drop messages from Outlook into File Explorer to create msg-files.

Step 2: Backup any folders marked with: On this computer only

If any of your folders of your mailbox in Outlook are marked with “This computer only”, you’ll need to copy or export the contents of these folders as well before resetting your cache.

These folders are likely to exist when you only have an IMAP account configured in Outlook 2013 or Outlook 2016.

A good method to find these folders is by switching to the Folder List Navigation in Outlook (keyboard shortcut CTRL+6). Common folders that are marked with “This computer only” are;

  • Drafts
  • Contacts
  • Calendar
  • Tasks
  • Notes

Extra Tip!
Configure Outlook to store the “This computer only” folders within a pst-file so you won’t risk losing them and also making it easier to back them up. For more details see: Don’t risk losing your Contacts and Calendar when using IMAP in Outlook 2013 or Outlook 2016

Step 3: Reset the cache of your account

Now that all your unique data from the cache is backed up, you can reset the cache in the following way;

  1. Open the Account Settings dialog;
    • Outlook 2007
      Tools-> Account Settings…
    • Outlook 2010, Outlook 2013 and Outlook 2016
      File-> Account Settings-> Account Settings…
  2. Select the Data Files tab.
  3. Select the mailbox for which you want to reset the cache.
    This will most likely refer to an ost-file, but for IMAP accounts in Outlook 2007 and Outlook 2010, this will be a pst-file.
  4. Click the “Open File Location…” button.
    If your ost-file is located in the default location, then this will open the following location in File Explorer;
    C:Users%username%AppDataLocalMicrosoftOutlook
  5. Close Outlook and wait for it to be fully closed (just wait 2-3 minutes to be sure).
  6. Return to File Explorer and rename the ost-file of your account to .old so it will now be called like; <filename>.ost.old
  7. Start Outlook again and it will automatically rebuild the ost-file. Give it sufficient time to sync (download) your mailbox again.
Reset view outlook for mac

Reset Outlook 2016 To Default Settings


Opening the file location of an ost-file via the Data Files tab in Account Settings. (click on image to enlarge)

Step 4: Restoring backed up items

If you backed up any data in step 2, then you restore these items after Outlook has finished syncing all your data.

How To Reset Outlook To Default Settings

If you backed them up as msg-files, then you can simply drag & drop these files back into Outlook.’

How To Reset Outlook 2016

If you created a pst-file, then you can connect to this pst-file in Outlook via;

  • Outlook 2007
    File-> Open-> Outlook Data File…
  • Outlook 2010
    File-> Open-> Open Outlook Data File…
  • Outlook 2013 and Outlook 2016
    File-> Open & Export-> Open Outlook Data File

Outlook On Mac Account Settings

You can then drag & drop these items to their correct folders within Outlook.

After a sync interval, these items should be available again within webmail as well, unless the items are stored within “On this computer only” folders.