There is a decidedly dishonest component to most spam. Spammers make no effort to match message content with a recipient's interests, and their messages frequently lie, claiming that the recipient has an association with the company or its partners or in some way requested information. Messages are sometimes designed to look like an actual exchange between two people that was mistakenly misdelivered in the hopes of sparking interest in some product or service.
Spam frequently offers instructions to opt out from receiving more messages; however, in many cases this is simply a subterfuge on the part of the spammer to confirm that your email address is good. By replying to such messages, you confirm that your address is a legitimate one. Following the directions provided will more than likely cause your address to be added to more spammer lists.
Spammers often try to hide their trail so their messages cannot be traced back to them. They purposely use false return addresses and forge header information. They seek out misconfigured systems that allow them to relay anonymously. More recently spammers have broken into systems and installed their own secret relay servers. Spammers commonly encode their messages or insert random letters to circumvent spam filters.
Some of the techniques employed by spammers have sideeffects that make the problem much worse than the act of spamming itself. In their scatter-shot approach, spammers send messages to email addresses they think are likely to exist whether they actually do or not. Some launch dictionary assaults on mail servers where they run through preassembled lists of names hoping to find a match with a user on the mail server.
General Configuration and Administration
Email and DNS
Local Delivery and POP/IMAP
Hosting Multiple Domains
Blocking Unsolicited Bulk Email
Transport Layer Security
Appendix A. Configuration Parameters
Appendix B. Postfix Commands
Appendix C. Compiling and Installing Postfix
Appendix D. Frequently Asked Questions