alt Hacker NewsI don't really remember many Windows 95 firsts. One I remember is the ability to switch users without logging off. MacOS famously copied that (with a 3D cube look).
I think they made something really revolutionary at the IE3 time. Their News and Mail app was an Explorer extension that placed an e-mail reader as the presentation of a folder full of folders of mailboxes and messages. You wouldn't see the extension, as the apps launched as applications, but that's what the implementation looked like from what I investigated back then.
Unfortunately, the idea was seemingly abandoned almost immediately. I would love to have such views on top of a user-space file system keeping messages, address books, and calendars in sync.
At my first ISP job, I eventually started using mh for mail. It was based on an awesome concept of sorting everything into directories and having procmail and various helpers to pre-process, including upon receipt and reading. I remember little of the details, but it was truly for the gung-ho neckbeard crowd, and it was well-suited for processing "large amounts" of mail (1993 style). I think MMDF was the MTA trying to do similar things in that vein. Meanwhile my boss was in love with PINE...
Of course, working at an ISP I could also telnet to our NNTP server and read Usenet on the local filesystem. Ugh.