This is largely a technical problem resulting from Email's unpredictability and lack of any receipt verification mechanism. While this is true of other non-real time communication mediums (like snail mail), that doesn't mean we shouldn't try solving it.

Improved spam detection increases the likelihood that an email will actually reach its intended recipient. In the 7 years I've been using gmail I've seen exactly one false positive (although there is some bias here as I've long since stopped checking my spam folder). But such technology has been slow to filter out to the less technically inclined ISPs and mail providers.

As far as actual verification, there are several ways to achieve this now. A popular technique is embedding a 1x1 pixel image with a unique id in its url. Unfortunately this is frequently abused by spammers looking for verification that an email address is good, so many email readers block images by default.

Any real solution is going to require some sort of trust mechanism or better make the procedure opt-in. Still, anything would improve upon the current situation where letters go silently into the void