20. sendmail: Setting Up Mail Clients, Servers, and More

IN THIS CHAPTER JumpStart I: Configuring sendmail on a Client 630 JumpStart II: Configuring sendmail on a Server 631 How sendmail Works 632 Configuring sendmail 635 SpamAssassin 640 Webmail 644 Mailing Lists 646 Setting Up an IMAP or POP3 Server 647 Setting Up KMail 648 Authenticated Relaying 650

Sending and receiving email require three pieces of software. At each end, there is a client, called an MUA (Mail User Agent), which is a bridge between a user and the mail system. Common MUAs are mutt, KMail, Thunderbird, and Outlook. When you send an email, the MUA hands it to an MTA (a Mail Transfer Agent such as sendmail), which transfers it to the destination server. At the destination, an MDA (a Mail Delivery Agent such as procmail) puts the mail in the recipient’s mailbox file. On Linux systems, the MUA on the receiving system either reads the mailbox file or retrieves mail from a remote MUA or MTA, such as an ISP’s SMTP (mail) server, using POP (Post Office Protocol) or IMAP (Internet Message Access Protocol).