Capital One, a large US-based bank and credit card issuer, stands out for sending by far the largest number of transactional emails containing personally identifying information (PII) to my spamtrap collection. :/ Capital One uses a number of ESPs, but its transactional emails are usually sent from Bigfoot Interactive, owned by Epsilon Interactive.
United Airlines, a major U.S. based airline with routes around the world, just sent a bulk email advertisement to an email address that never heard from it before. The spamtrap address was closed in 2004. Nonetheless, the email contains a name and a OnePass (United’s frequent flyer program) number or scrambled version of it in the header and a masked version in the message body. This suggests one of two possibilities: that United is emailing uncontacted email addresses after years of ignoring bounces and undeliverables, or possibly that United hired an e-append firm. The ESP is Responsys.