I receive multiple Economist spam emails a day, and none of them are from <>@economist.com, or a marketing firm. The TLDs alone give them away: <>@<>.faith, <>@<>.date, and so on. The links in the emails also go to the odd TLDs or to clearly bogus domains.
The links in the emails go to the odd TLDs, where they then redirect a few times ending up at The Economist with what appears to be affiliate tracking information in the URL, which I presume is so that the spamming affiliate will get paid if I subscribe at that point.
If I can figure out what email address @economist.com to report this to I'll send them a sample of one of the mails and the affiliate tagging information and hopefully they'll kick that affiliate out of their program.