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 481,273 websites that are Sender ID Customers. We know of 356,611 live websites using Sender ID and an additional 124,662 sites that used Sender ID historically and 123,095 websites in the United States.
Get a list of 481,273 websites using Sender ID which includes location information, hosting data, contact details, 356,611 currently live websites and an additional 426,965 domains that redirect to sites in this list. 124,662 sites that used this technology previously and 123,095 websites in the United States currently using Sender ID.