Verizon, one of the largest telecommunication companies in America, has sent email to several of my spamtraps in the past few weeks. These emails solicit the business of companies that are not associated with those spamtraps, but whose company names might plausibly belong to the email addresses that received the spam. No ESP was involved; Verizon sent this email from their own IPs.
U.S. and global telecommunications giant Verizon just sent an advertising email to a spamtrap that was closed in 2003. This spamtrap has not previously heard from Verizon. As the advertisement urges the spamtrap to switch to Verizon from (presumably) another telephone and Internet service, this cannot be email to a customer. The email also makes no claim to be opt-in. The ESP is Sendgrid, whose authorized use policy explicitly requires that bulk email sent through their service be opt-in only.