Seeing how DNS prefetching is the new fad with browsers, I reckon there’s an easy way to confirm valid addresses of webmail service users:
- Control a DNS to assign unique hashed hostnames.
- Integrate links to hashed hostnames in spam mails.
- If the recipient uses current Chrome, Firefox, etc:
- The DNS prefetcher will resolve the host name,
- Giving you a confirmed hit for the address in your logfiles, since your unique hostname gets resolved.
Kind of reminiscent of the whole “oh, we can have e-Mails with HTML, let’s put in images!” affair. The only thing that might be a bit of a problem for a spammer is getting a domain with DNS server control.