Maildir is a the mail directory which contains many folders and subfolders of an email. But if you want to open Maildir on Outlook then it is not possible without a software. So if you are looking for a professional software then Maildir Migrator would be the option for you.

This software converts the maildir files to PST, MBOX , EML, and to various other file formats. it is quick and fast. This software even converts the sub folders like tmp, cur and new to whatever file format in which you want to convert. 

Don't waste your time looking for the software on the various websites. Just download it from the official website of Data Recovery Solution and easily convert maildir to PST. Once you convert the Mail Directory to PST format then you can easily view it in MS Outlook.