I used to use the NME website, which was a weekly music paper in the UK, back in the day.
It had forums and free webmail, so I had had an nme.com address that made me feel kinda cool (I was a teenager and music was very much my identity).
Then they cancelled the webmail and that was that. All my teen emails gone forever. I'd love to get them back, and who knows,they could be sitting on a server somewhere, but I doubt it.
Oh, also Bebo. Posted a lot on that precursor to Facebook and now it's all gone.
I tried to join when I got banned from Reddit permanently after like 12 years for ban evasion (using a throway account). I joined the waiting list for an invite but still waiting. That's when I discovered Lemmy, which I'm quite liking. Never heard of Piefed. Is it similar?