>I need to validate a list of thousands of e-mail addresses. Does anybody know of a way to easily check whether the addresses are deliverable without actually sending a message? (something like the "finger" command??)

Not really. You could try to determine if the host exists (eg ping their host to see if it exists), but not all sites implement finger, and not all hosts are mail servers. Short of sending a mail packet and seeing if it bounces, you can't easily determine if the email address is valid; it may just be a forwarder (eg I have an account that acts as an alias for my actual account; mail sent to the alias arrives at my real account.)