The Sender Policy Framework is an open standard specifying a technical method to prevent sender address forgery.
http://www.open-spf.org/
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Get access to data on 166,844,073 websites SPF Customers. We know of 118,761,713 live websites using SPF and an additional 48,082,360 sites that used SPF historically and 8,626,245 websites in the United States.
Get a list of 166,844,073 websites using SPF which includes location information, hosting data, contact details, 118,761,713 currently live websites and an additional 5,063,423 domains that redirect to sites in this list. 48,082,360 sites that used this technology previouslyand 8,626,245 websites in the United States currently using SPF.
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