It's probably for the best. As recently as 2016 (and probably more recently; that's just the last time I tested this), they weren't even validating SPF records on their email-to-SMS gateway. You could spoof the "From" address to any email address you fancied and your messages would go through, appearing to be from that sender. Back in high school, my childish self had a field day showing off my phone's SMS inbox filled up with spam Viagra ads that were "sent by" Hillary Clinton's "hacked" email server.
It's not as funny in hindsight, given the unexpected results of that election, but at the time, it felt like top-tier humor.