> Outlook has an odd limit on the number of columns.
I've had problems with IE itself in the ~<1024 cells range (it was about 900~1000 IIRC. More cells, and it simply drops either the extra cells, or the table itself, I can't recall). I seem to remember the value was actually round in some way.
Use case was a horizontally scrollable day-based timeline, and the user decided to look at more than three years worth of data, which worked just fine everywhere but in IE.