Comment by yason

I have most of my friends using some messenger app and based on that I run―because I basically have to run―Whatsapp and Signal myself. But those are all people I know. What would you use but SMS when contacting people you don't?

Typically, if I try to reach someone but they don't answer I'll follow up with an SMS to explain what I tried to call for. If it's a co-worker, or an acquaintance, I'll send an SMS to make sure they receive my message. SMS is more reliable, doesn't require you to know which apps the other party runs, and it comes through to the recipient as SMS is a basic service in the telecom networks.

When I get to know a new person there's a transition to "oh, you're on $APP too", and I might starting moving non-urgent messages to $APP. But if you don't know the other party well or there's a question of reliability, what is an alternative backbone for messaging if not SMS?