[gerdesj]

In email the From: address rarely delivers the mail. From: and To: are the ones that you see in your mail client and correspond to the addresses on the letter within.

For example here are some headers from some spam I received:

  From: "Jeremy Adamson" <[e-mail]>
  Reply-To: "Jeremy Adamson" <[e-mail]>

From: is what I see in my client and Reply-To: is where a reply would go to.

This one is much better, note how I'm BCCd and To: is complete bollocks:

  Reply-To: [e-mail]
  From: Dr Faruk Ahmed <[e-mail]>
  Subject: MANAGER AUDIT AND ACCOUNT DEPT
  To: undisclosed-recipients:;
  BCC: <[e-mail]>
  Return-Path: [e-mail]

Given that Reply-To and Return-Path are in different domains, where would a reply go to?

[JamesBarney]

What about an out of band verification by the carriers?

Basically a large registry. When I call someone I tell t-mobile who I'm calling, and they register it. Then on the receiving end Verizon checks with T-mobile or a central registry, and says yep James's number is calling this number. Then it marks it as a verified call.

[gerdesj]

Bear in mind that it is not in a carrier's (financial) interest to drop a call. Carriers are not required to verify CLID either.

There are lots of good things that telephony could be required to do but they are not and they wont.

[Splines]

iOS/Android could do something like this. You register your number with Apple/Google and link your account with them. When you call someone you set a field on your account that you're calling someone. When the person who you're dialing gets rung, their dialer can look up Apple/Google and see if that number was indeed calling them, and add a "verified" checkmark to the call.

This leads down a privacy/metadata rabbit hole, but there are probably ways to make this a lot better. In any case, the phone OS can do some out-of-band signaling and just avoid dealing with the carriers altogether.

Although if you're doing all that then why not just make a call using voip...