How does the spam filtering system work?
The spam filters are necessarily dynamic in nature because they need to react to keep up with the changing tactics of spammers. The determination of whether a message is spam (junk) or ham (good) is based on not only sender's network reputation, but also on the content of the message. The system will identify common characteristics of reported spam, such as phone number, email address, website address, etc., and filter future message to look for those items that are now associated as spammy content.
Why are good messages being marked as spam?
A message gets marked as spam if it comes from a company or service that has a questionable reputation for sending mail, or it could be because of certain spammy phrases, phone #'s, websites or email addresses contained within the message.
Why should I train the spam filter?
The filter takes advantage of user input in order to determine whether or not a questionable message is spam. What is spam to one person is a desired message to another person. Training the filter (by marking a message as “Spam” or “Not Spam” helps it to understand what you consider a valuable message.