Except that mail has no authentication which is something I would need.
No function has it's own authentication, you do that yourself at the beginning of the request.
Pass a password to the script in the request and verify that.
Except I believe it's not a good idea because
I believe I've heard that BL doesn't work with HTTPS? So It might not be smart to do that
Blockland isn't the only thing I host off of the same machine, you know.
Which only makes my point even more relevant?
A tiny application listening to TCP requests and sending SMSs is insignificant compared to everything you're hosting.
If adding that tiny of a thing kills your resources, then your resources are already dead