In our shared cloud server app we detected sudden break in email sending, upon looking at log I stumbled across
"ReferenceError: Bodyparts is not defined"
I found that
var bodyParts = new Bodyparts();
now should be
var bodyParts = new Backendless.Bodyparts();
I updated my code and now it's working as before (previous version of code was taken directly from documentation, nothing fancy on my side).
But I must say - guys, it's not cool to change your SDK without any warning.