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 190,445,749 websites that are SPF Customers. We know of 133,366,778 live websites using SPF and an additional 57,078,971 sites that used SPF historically and 9,570,379 websites in the United States.
Get a list of 190,445,749 websites using SPF which includes location information, hosting data, contact details, 133,366,778 currently live websites and an additional 6,567,203 domains that redirect to sites in this list. 57,078,971 sites that used this technology previouslyand 9,570,379 websites in the United States currently using SPF.
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