Beyond web logs

Everyone hates SPAM! So much so, that people will change their ISP providers or email host to get better protection from SPAM. As a result, companies like AOL and MSN spend tons of money coming up with new ways to provide "better" spam protection to their subscribers to reduce their attrition rates.

PAM filtering methods:

1. Phrase filters - watch what you say! Many email servers use a list of unacceptable or offensive word and phrase lists and will reject or place the message in a junk folder upon a match, so watch what you say, or your message could be rejected.
2. Connection Checks - poorly configured email servers can cause loss of messages. This is most likely out of your control (unless you are a server admin), but just be aware that when email servers talk to each other, some are very picky about allowing a connection and may reject it if the source server does not "check out" properly.
3. Statistical Analysis - this is used to catch some of the techniques used by spammers like many repeated words or a bunch of unrelated words stuffed in the message (usually to try to throw off the spam filters). Your message can become a victim of this if you do something like copy and paste a data file into the body of your message or if you were to insert a data file (like a mail list or spread sheet) into your message, as opposed to attaching the file.
4. Domain Black Lists - Your ISP does not like your friend's ISP! - server administrators will use a list of trusted (and sometimes not-so-trusted) domain and/or IP address lists to filter incoming messages. If you happen to be using one of the "bad" service providers, your messages could be dropped. Watch the company you keep!
5. HTML code checking and filtering - Don't get too fancy with your Html email messages. Many servers are set up to reject messages that contain certain html code. Especially scripts, deceptive URLs or encoded text.
6. Discretionary Blocking by email address, domain, or IP block. - Most email server gives the admin the power to place a block in their server to deny access to any server or domain of their choosing.
7. Server Rule Sets - in addition to all of the above obstacles, most email servers can be custom configured with rules that will redirect or delete messages on just about any content that you can think of! A incorrectly coded rule could create a virtual sink hole for messages.
8. & More you can add in comments...