Some Basics about SMTP

Many of the following options involve SMTP. SMTP stands for Simple Mail Transfer Protocol. This protocol is the de facto standard for sending and receiving email messages.

Due to SMTP’s simplicity, it is a relatively vulnerable protocol. It is often abused by spammers who wish to send email messages with falsified headers — messages that appear to be from somewhere they are not.

These options are important to define, as they will help prevent spammers from launching attacks on and from your server. As many spam messages can be sent within a short period of time, these attacks are costly to your bandwidth.