Hi,
No, not at all. The domain owner determines what servers they want mail to originate from. If the domain owner doesn't want people to be able to use webmail, they'll adjust their spf record appropriately. If they do, they can also setup the spf record to allow this.
For instance, aol.com:
aol.com text "v=spf1 ip4:152.163.225.0/24 ip4:205.188.139.0/24 ip4:205.188.144.0/24 ip4:205.188.156.0/23 ip4:205.188.159.0/24 ip4:64.12.136.0/23 ip4:64.12.138.0/24 ptr:mx.aol.com ?all"
The ?all means that 'SPF queries that do not match any other mechanism will return "neutral". Messages that are not sent from an approved server should still be accepted as if the SPF record did not exist.'
But for gossamer-threads.com:
gossamer-threads.com text "v=spf1 a mx ip4:64.69.64.0/24 ip4:64.180.111.209 ip4:64.180.111.210 ip4:64.180.111.212 -all"
The -all means that if you were using @gossamer-threads.com in your profile on a different IP, then you would get rejected/marked as spam by an spf enabled server.
But it's up to the domain owner to set the policy for how the domain should be used.
Cheers,
Alex
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Gossamer Threads Inc.