2TB SQL/Oracle database back then? Sure.
I'm utterly baffled about these limits. My Oracle database hit 1TB - back in 2001 on Windows NT 4, and with no sign of getting anywhere a limit.
That's because your 1TB database was made up of a whole bunch of 32-bit .DBF files, almost 100% surely strung over multiple drive letters (mount, er, "reparse" points didn't become a thing until Win2K).
Doesn't Outlook use SQL server as it's backend? I'm pretty sure that even back then, SQL server could go over 2TB.
Exchange (not Outlook, that's the client) does use a tuned variant now, but way back when, it was the JET engine, baby.
And in 2012, we still had that Oracle database running on Windows 2003, then over 200TB and growing by at least 2TB a month.
a) Yeah, Oracle licensing remains as transparent and platform-migration/upgrade friendly as ever /s
b) I always knew paypal had some humble beginnings, but ... /s /s