My guess would be it's to build up reputation of the sending accounts, by being "connected" to trusted, aged, accounts? However, the combination of garbled text

My guess would be it's to build up reputation of the sending accounts, by being "connected" to trusted, aged, accounts? However, the combination of garbled text + number @ large provider on its own should be pretty suspicious by now. Another idea is some kind of affiliate marketing / pumping attack, but I don't see ads.