I spent two years trying to work out why my parents never got Signal Messenger messages until they left thier house (roamed from WiFi to mobile data). We suspected it was mobile broadband/DNS problems, as the issue eventually resolved itself when fibre became available.

I was helping a friend today; debug why he was getting connection refused for a certain site he was browsing to. I was stumped (it worked on his mobile data connection), and alarm bells rang when he said he also has issues with Signal Messenger, only getting messages when he leaves the house. And in fact it happens with emails too, he said. This happens on his (and his wife's) Android handsets.

Though, he has Fibre. So maybe the wireless broadband conclusion was a red herring. What on earth is Spark doing to be blocking these safe/essential services?

With this new info I was intrigued and we are looking at Net Shield as a possible cause. Though won't have info on that for a few hours.

Spark were NEVER able to diagnose or resolve the original issue. But it seems common enough.