Even email spammers don't do this as far as I know. They just send out millions of spam emails to random generated email addresses, and discard any that are returned.
What I mean is, there would have to be some method to sniff out current email addresses by interrogating email servers or web-mail servers, but those server administrators would work very hard to protect the privacy of their customers.
The hard way would be to send a quick query email to each address, and any that are returned unread will be out of date. But of course, you may not want to contact all of them.
You don't say in what context this is, eg an office environment, your own business, or just your personal email account, but I don't see any easy way. For my personal account it is easy. I just delete those I don't want any more, and keep those I do, eg relatives, friends, known recent contacts, etc.
Mark
hello guys, I hope you can help.
many of my outlook contacts e-mail addresses are now out of date.
--> Is there an add-in or program which can scan through my contacts [either in Outlook or in an exported file], search out, verify and delete the e-mail addresses which are no longer in use please?
I would be grateful for any tips from the experts.
Best,
Jon

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic