Well we were a small startup, and the idea of using AIX was a non-starter. Solaris was lovely, but our E250 was only for mail, and in hindsight we should have stood up a FreeBSD server with dovecot or something instead of a system that we migrated off of a year later.

We did use NT/2K internally but that was because we had some who insisted on using SMB via Windows.

Such fun times. The nix and nix-like OSes were spreading like fire. I never would have thought I'd ever wrangle them for the majority of my career.