Sender ID is an anti-spoofing email framework heavily based on SPF.
https://en.wikipedia.org/wiki/Sender_ID
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Get access to data on 455,262 websites that are Sender ID Customers. We know of 332,493 live websites using Sender ID and an additional 122,769 sites that used Sender ID historically and 119,358 websites in the United States.
Get a list of 455,262 websites using Sender ID which includes location information, hosting data, contact details, 332,493 currently live websites and an additional 453,498 domains that redirect to sites in this list. 122,769 sites that used this technology previously and 119,358 websites in the United States currently using Sender ID.