You need best software like
SysBud NSF to PST converter that converts all single email to Outlook PST format. It not only migrate the email, even contact, calendar, task, and many mail stuff. User can install and run the application on Window based operating system and perform error-free migration from NSF to PST. This Lotus Notes converter allows user to convert NSF file in PST, Office 365, Live Exchange, MBOX, EML, HTML, MHTML, and RTF. Not only this, you can also export contact and calendar in csv and ical format respectively.

As a test, you can use the demo version of NSF file converter and export first 20 emails from each mailbox.
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Lotus Notes to Outlook Converter