[SoftTalker]

Hotmail ran on Unix for years after Microsoft acquired it. It took quite some time for them to migrate it to Windows server.

[hylaride]

Yeah they ran on FreeBSD, but despite multiple attempts IIRC they didn't fully pull off the migration until Windows 2000. There was a relatively honest paper they wrote about the transition: https://web.archive.org/web/20021021164226/http://www.securi...