Shutdown Mail Server for De-Spamming ? I don't think so.

De-Spamming The Inbox: The Hard Way
This article shows that turn off mail server for 2 days will reduce 97.5% spam.

I think this way is useless, many of the comments also stand opposite opinion.
Because:
1. Spammer never use real Email, never recive bounce mail
2. Spammer don't care Email valid or not
3. Email list will increase, never decrease