apt-get install postgrey netstat -anp | grep 60000 tcp 0 0 127.0.0.1:60000 0.0.0.0:* LISTEN 18478/postgrey.pid
In /etc/postfix/main.cf add to "smtpd_recipient_restrictions ="
Lists the automatically whitelisted servers:
reject_rbl_client bl.spamcop.net, reject_rbl_client relays.ordb.org, reject_rbl_client sbl-xbl.spamhaus.org,
SPF stands for Sender Policy Framework. It's a way for your server to verify if a connecting client is supposed to be sending mail for the domain it claims to be sending mail for. It works by checking a special DNS record that domain owners create for this specific purpose. For more info on the Sender Policy Framework check out the Openspf site
Significantly reduce the amount of spam
- whitelists: accept mail from known, trusted senders.
- blacklists: refuse mail from undesired senders.
- challenge/response: allows unknown senders which aren't on the whitelist or blacklist the chance to confirm that their message is legitimate (non-spam).
- tagged addresses: special-purpose e-mail addresses such as time-dependent addresses, or addresses which only accept certain kinds of communication. These increase the transparency of TMDA for unknown senders by allowing them to safely circumvent the challenge/response system.
This methodology has the advantage of being very selective about what it allows in, while at the same time permitting legitimate, but previously unknown senders to reach you.