How To Use Outlook With a Mailbox Larger Than 50GB

• If your Mweb mailbox is larger than 50GB, Outlook may not sync all your mail because of a built-in file size limit. You can safely increase this limit in Windows to keep using Outlook without losing mail.

  Step 1: Check Your Outlook Version

  These steps apply to Outlook 2010, 2013, 2016, 2019, and Microsoft 365 for Windows.
  If you’re using Outlook 2007 or earlier, please upgrade before continuing.

  Step 2: Increase the Outlook Data File Size Limit

  Outlook stores your emails in a local data file (PST or OST). By default, the limit is 50GB. To raise it:

  1. Close Outlook.
  2. Press Windows key + R, type regedit, and press Enter.
  3. Go to:

     HKEY_CURRENT_USER\Software\Microsoft\Office\<version>\Outlook\PST
     

     Replace <version> with:

     • Outlook 2016, 2019, 365 = 16.0
     • Outlook 2013 = 15.0
     • Outlook 2010 = 14.0
  4. Right-click PST, select New > DWORD (32-bit) Value.
  5. Name it MaxLargeFileSize and set the value (in MB):
     • Example: 102400 = 100 GB
  6. Create another DWORD named WarnLargeFileSize and set it slightly lower (e.g. 95000 = 95 GB).
  7. Close the Registry Editor and reopen Outlook.

  Step 3: Keep Performance in Mind

  • Outlook may slow down if your data file grows beyond 100GB.
  • Archive old mail into a separate PST file.
  • Use folders and rules to manage large inboxes.
  • Turn on Cached Exchange Mode for smoother performance.

  Step 4: Use Webmail for Very Large Mailboxes

  For mailboxes exceeding 100GB, you can access your email directly at https://www.mweb.co.za/webmail. Webmail connects straight to our servers and is not limited by Outlook’s local file size restrictions.