It's not for fun. They are hijacking a trusted server (Zendesk) to smuggle phishing links past my spam filter. Since Zendesk blocked the text relay, their bot is now just spamming signups as a side effect of the failed exploit.
[Ref](https://support.zendesk.com/hc/en-us/articles/8257723564186-...)
[Ref 2](https://darknetsearch.com/knowledge/news/en/zendesk-ticket-s...)