Switching from IBM Notes (HCL Notes) to Outlook 365 is common nowadays, but manual migration is complex and risky. The safer route is using an automated NSF to PST converter.
I personally recommend eSoftTools NSF to PST Converter because it lets you convert NSF files directly into PST. Once you have PST files, importing them into Office 365 (or Outlook 365) is straightforward using Microsofts native Import feature.
The tool preserves your folder hierarchy, email formatting, attachments, contacts, and calendars during the entire process. That means no data loss or corruption, and the transition feels seamless.