Perhaps you have configure your own postfix server to get rid of spam?
If you have checks against relays.ordb.org configured in your mail server or spam filtering software, you're now blocking 100% of your inbound mail
3/26/08 Update: ORDB has "listed the entire world" -- returning any query with a "listed" response. The result is that if you still have ORDB in your mail server config files, you're now blocking 100% of your inbound mail. For anyone still trying to "use" ORDB, you're not going to receive any inbound mail until you disable queries to it.
Read more here.
HowTo reconfigure postfix:
1) In the file "main.cf", remove the line: reject_rbl_client relays.ordb.org,
2) run: /usr/sbin/postfix reload
3) Now you will get eMail again!