Yeah, I’m quite sure it’s a deliberate activity to dissuade against private email servers. Keep everyone’s email “in the club”. Once you’ve got this much working you need a whole suite of tools to deal with the HUGE amount of spam you need to filter. It can be a hell of a lot.
Yes, came to say the same. It’s very easy to get a voip number in most countries. But many places that want to use it for ID purposes (finance etc including paypal) will know the voip allocations and block them.