I am using Outlook 2010 with Conversations view, sorted by date, descending. I think I may have removed a default column when playing around and I don't recall whether I put it back or not, but I do know that whether or not I did the behaviors I've described are consistent between NVDA and Window-Eyes, both their latest versions.
The columns I have on display are one that switches you out of Conversations view, but not back in, and that has no hover text. The rest are labeled with hover text and follow from left to right after that switch column in the following order: Importance, Icon, Attachment, From, Subject, Received, Size, Flag.
I worry a lot. . . I worry that no matter how cynical you become it's never enough to keep up.
~ Trudy, in Jane Wagner's "Search for Signs of Intelligent Life in the Universe"