Keeping Your Server Off Black Lists
From Computer Tyme Support Wiki
Most spam filtering companies do the best they can to pass good email. Often there are problems where good email gets blocked. One of the factors that contributes to good email getting blocked are email servers that aren't properly configured. Doing it right makes a big difference and many easy steps can keep you from getting blacklisted. And it makes your server a candidate for white listing which will get you through some spam filters faster.