Modify registry entries, follow these steps:

  1. Click Start, and then click Run, type Regedit, and then click OK.
  2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\PST (x.0 corresponds to the Outlook version: 16.0 = Outlook 2016, 15.0 = Outlook 2013, 14.0 = Outlook 2010)
  3. Click PST, and then right-click MaxLargeFileSize in the right pane.
  4. Click Modify, and then type the value in the Value data
  5. Click OK.
  6. Right-click WarnLargeFileSize, and repeat steps 4 through 5.

Note: you may have to create the registry values if they do not exist. If the registry values do not exist, follow these steps to create them:

  1. Click Start, click Run, type Regedit, and then click OK.
  2. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook (x.0 corresponds to the Outlook version: 16.0 = Outlook 2016, 15.0 = Outlook 2013, 14.0 = Outlook 2010)
  3. Right-click Outlook, point to New, and then click Key.
    PST
  4. Type PST, and then press ENTER.
    PST 2
  5. Right-click PST, point to New and then click DWORD
    DWORD
  6. Type MaxLargeFileSize, and then press ENTER
  7. In the Edit DWORD Value window, choose Decimal and type the value in the Value data box, and then click OK.
    Value
  8. Repeat steps 5 through 7 to create another DWORD WarnLargeFileSize, and then close the registry.

Value for registry entries should be set in either bytes or megabytes and you will need to calculate it first. You can find predefined values for 100 GB and 95 GB below:

 MaxLargeFileSize should be 100 GB = 102400 MB

 WarnLargeFileSize should be 95 GB = 97280 MB