One of the ways to differentiate between MS Outlook and Lotus Notes is by comparing the companies that hosted the two servers. While Lotus Notes belongs to IBM, MS Outlook belongs to Microsoft. Both can be installed on a computer so that users can have access to their mail files at any time.
Both MS Outlook and Lotus Notes store information on their separate data files, but different formats are used to store these files; while MS Outlook uses PST format, Lotus Notes uses NSF format. Before you can have the Lotus Notes application installed on your computer, it must be bought, whereas MS Outlook can be installed freely, but it will require that you have some applications installed.
Another difference is that Lotus Notes needs constant maintenance. These are the reasons why Lotus Notes is quite expensive compared to MS Outlook. The fact that Lotus Notes supports more operating systems than MS Outlook is another difference between the two.