Sprinkled whispers ground or whole I wake the tongue and warm the sole from distant lands in jars I dwell turning simply into swell I'm not the meal but make it nice what am I?

A greeting. Or a departure. Electromagnetic. Kinetic. Poetic

I bind what’s loose, I link what’s far. I guide the pulse just like a star. Silent myself, I let signals fly. What is it through which currents sigh?

A metal guard stands at the door, Holding letters galore, Rain can't intrude, Nor just any prying dude, Your messages safe, it swears to store.

If you're outside, you can talk as loud as you want, but you'll need to communicate with this if you want your bill to paid.