Google recently proposed a new method for verifying that an email address exists without sending a verification message to the address. They are calling it the Email Verification Protocol and there is an associated Internet Draft.
The idea is that the verification process all happens within the web browser at the point of address submission instead of being split between the website and wherever email lives. Not using email to verify the validity of an address removes friction such as sending delays and message filtering false-positives.
Google are currently running a trial with Chrome and Gmail but other providers may also apply.
If the protocol can be further developed to work at internet scale and not be limited to a handful of large hosted email providers then this will a useful addition to the ecosystem.