The default file size limit for Outlook data file (.ost) is 50GB. To change file size limit to 100 GB, add following keys to the registry usind cmd or regedit.
REG ADD HKCU\Software\Microsoft\Office\16.0\Outlook\PST /v WarnLargeFileSize /t REG_DWORD /d 102400 /f
REG ADD HKCU\Software\Microsoft\Office\16.0\Outlook\PST /v MaxLargeFileSize /t REG_DWORD /d 107520 /f