When i open file with code
using (MsgConverter converter = new MsgConverter(@"distlist.msg")) { IMail email = converter.CreateMessage(); }
I get error. But this file can contains text/rtf/html in Notes section
Guide to create Distribution list .msg file https://www.scrubly.com/blog/how-to-outlook/how-to-create-edit-and-manage-outlook-distribution-lists/
then save it with "Save as..." -> Outlook message
As this is not a regular message, I don't think Mail.dll supports this kind of content.