There was also Outlook Express.

It could do NNTP feeds integrated with e-mail, an outgrowth of previous work on IE3-era Windows News and Mail (which was an architectural masterpiece - a Windows Explorer view of a folder full of messages, populated from the mail and news feeds)

I wish we had something like that in Gnome - processes that sync my IMAP mails to local Maildir-like folders (dynamically populated, with download-on-open, perhaps) and a view that shows e-mails. Same for iCal feeds - make it a way to view specific kinds of content.