Sendmail on Ubuntu sending multiple blank emails without me triggering them

My goal was to create a simple text–> email mechaism using twilio. I installed a LEMP stack including sendmail onto an Ubuntu server.

I got the thing working–I can text my twilio number and get it in my inbox!–but, unfortunately, I also get tons of blank emails from my own site (it has no content–literally used just for the purposes of this text to email configuration).

These emails aren’t being triggered via twilio, per my twilio dashboard, so I assume there’s something weird happening with sendmail.

Any ideas what could be triggering these emails to fire out of the blue? I have like zero security–could that be it? What should I install to fix it?