Hard to beat Outlook 2007 which had some "smart tags" feature that all referenced "5iantlavalamp.com", and things started breaking when that domain expired.
It's hard to remember many details from almost 20 years ago, I just remember coming across it in email spools while writing anti-spam analysis scripts. Only mention I can find nowadays is https://www.experts-exchange.com/questions/22812691/What-is-....
I was working in anti-spam at the time, so I was eyeballing a lot of raw email dumps and writing analysis scripts for "anomalous" urls, so it popped up fairly frequently.
The primary problem is we can't search through time via WayBack Machine where a lot of these things have gone. Took me a while the other day to surface the Choco-Banana Shake Hang which Microsoft deleted from their production site.
Ah I misremembered one thing, nothing broke because it wasn’t even an existing domain when they used it. That was a different Microsoft domain I was thinking of.