OP didn’t say whether the distribution groups were in WLM local contact folders or a central ‘old’ outlook.com one.
Windows Live Mail was a surprisingly good successor to the old Outlook Express and allowed contacts and distribution lists to be stored centrally (as well as locally) and accessed via MSFT's special Deltasync protocol. Outlook could also access them via its 'hotmail connector' addin. However support for deltasync was switched off last year on the WLM server backend as users were moved to Outlook Mail.
When virtually all outlook.com accounts were moved during 2016 to Outlook Mail running against an Exchange Server backend, central contacts and distribution groups were preserved – with the exception that the contact name was replaced by the email address (so a distribution list was essentially two columns, each containing the email address). Microsoft also screwed up the links between items in a distribution list and the same items in the underlying contact list, so updates to the former could sometimes give odd results.
As previous posters have noted, there is no way whatever to export distribution lists via CSV, from either central or local lists.
Unsurprisingly, Outlook (even Outlook 2010) is the best tool to access the new Outlook Mail Exchange Server accounts. If you are running an old version of Office (Office 2010 or earlier), you can buy second-hand Outlook 2010 for around £50 and hope that the licence is a valid one. If it is, it is probably used to the limit of two installs, but a phone call to Microsoft can fix that quite legitimately.
Beware though of mixing Office 2010, 2013 and 2016 installs. 2010 was installed via MSI, 2013 was installed via “2013 click to run” and 2016 by “2016 click to run”. Even the latter two are not interoperable! : the regular updating process gets very upset, and installing e.g. Access from one de-installs stuff from the other.
Having fired those broadsides against MSFT, I am equally obliged to day that running full O365 email using Outlook makes any other email service (including Google Gsuite) look pedestrian, and this mostly applies also to mobile clients that use the light-weight EAS* protocol. Unlike Outlook Mail (which, as I said, also runs on Exchange Server at the backend), the user gets access to most of the voluminous and very comprehensive settings of Exchange Server.
* instead of Exchange Server’s gold-standard MAPI over HTTP that, among other things, also synchronises distribution lists properly! The only clients that handle shared distribution lists reliably are Outlook and the O365 webmail client (essentially the same as the Outlook Mail one). In the Google world, you even have to create new Google groups and populate them to handle personal distribution lists.
Zen from May 17. PN Business account from 2004 - 2017
