there are hundreds of possible causes, but usually it comes down to "someone at your ISP did something stupid and hasn't realised it yet."
like sending you an email to congratulate you for migrating from ADSL to FiberToTheCurb... just after they delete your mailbox, because that's standard procedure when an ADSL account is closed.
@Nikolai_Kingsley lol that sounds like you might be speaking from experience? :)
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