- Open run command by pressing Windows + R keys.
- Please close the Outlook application then Then type "regedit" on the run command.
- Open the HKEY_CURRENT_USER
- Go to "Software".
- Then "Microsoft" Folder.
- Then "Office" folder.
- Then look for "Office 16" folder.
- Open 16.0 then Outlook > pst folder.
- Please right-click the PST folder
- New
- DWORD (32-bit) Value
- Please name it "MaxLargeFileSize"
- Right-click on it then click modify.
- Click Decimal.
- Then put the value 4294967295
- After that "OK".
- Then right-click PST again.
- New
- Same proces DWORD
- Rename WarnLargeFileSize
- Right-click on it then click modify.
- Click Decimal.
- Value 4090445042
- Then click "OK".
- After that close everything then Open Outlook.
The new max size should be 100GB