I'm referring to a time when the Internet backbone was slow and intermittent. You're describing the last-mile situation. JMAP offers a solution for intermitten

I'm referring to a time when the Internet backbone was slow and intermittent. You're describing the last-mile situation. JMAP offers a solution for intermittently connected devices (phones) which expect notifications and messages from Internet services. I expect TMTP will do the same; it's far from final. (I'm the author.)