uniqueness, on one way or another, does not imply you're a real person.
those systems probably don't even rely on fingerprinting for those decisions - you just can't deny someone acceess to a service because "they're unique", you're opening a can of worms.
entities that do deny access based on fingerprinting actually do it based on same fingerprints corresponding to a marked visitor (like checking behaviour and marking all subsequent visitors with that fp as bad) - but it's a headache.
what you describe usually has more to do with your IP (range, usage type, country), your useragent or added/modified headers (check any extensions that do this)
i had exactly this happen some years ago when i added a `'` in the UserAgent to test a site for SQL injection and forgot to remove it.
Gmail has a blackbox ML that takes SPF and DKIM into account, but with a certain scoring that might not matter that much compared to said IPs reputation in their system.
> SPF attests that the mail was sent by an IP address that is authorized to send for a certain domain.
Yes, but SPF ties the IP address only to the Sender address (MAIL FROM) - so utterly useless in stopping phishing emails for example, if attackers can use said domain in From address.
> DKIM attests that various headers, usually including the From: address, are approved by the owner of the domain.
As the From address (and implicitly domain) is the one people see (and trust) DKIM in a way should matter more.
Also, misconfigured SPF records happen from time to time (on big domains actually), where bad actors can then take advantage of them and abuse delivery, much harder for a DKIM private key to end up in the wrong hands.
those systems probably don't even rely on fingerprinting for those decisions - you just can't deny someone acceess to a service because "they're unique", you're opening a can of worms.
entities that do deny access based on fingerprinting actually do it based on same fingerprints corresponding to a marked visitor (like checking behaviour and marking all subsequent visitors with that fp as bad) - but it's a headache.
what you describe usually has more to do with your IP (range, usage type, country), your useragent or added/modified headers (check any extensions that do this)
i had exactly this happen some years ago when i added a `'` in the UserAgent to test a site for SQL injection and forgot to remove it.