Also started migrating old accounts in free time.
Now its pretty easy to tell the source of leak by email addresses as well as sources of spam.
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Per-account alias might sound much, but using sieve filtering [1] is amazing, and you can get a comprehensive filtering solution going with 'envelope to' (the actual address receiving the email) + 'header to' (the recipient address you see, sometimes filtering rules don't filter for BCC or sometimes recipients are alias instead of your actual email) that are more comprehensive than normal filtering rules to sort your emails into folders.
[1]: https://datatracker.ietf.org/doc/html/rfc5228
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Amusingly, I've managed to recover old accounts from emails that contains my old passwords with demands for crypto payment, it just provided me enough help to recall old variations of my passwords.
I wouldn't have thought cats were domesticated 10,000 years ago, why is it implied that's a general assumption?