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 462,429 websites that are Sender ID Customers. We know of 327,060 live websites using Sender ID and an additional 135,369 sites that used Sender ID historically and 116,923 websites in the United States.
Get a list of 462,429 websites using Sender ID which includes location information, hosting data, contact details, 327,060 currently live websites and an additional 338,747 domains that redirect to sites in this list. 135,369 sites that used this technology previously and 116,923 websites in the United States currently using Sender ID.