Week 3 Blog

Week 3 Course Blog

Introduction

This week was all about electronic mailing and the architecture of electronic mail with Linux. Not only did we learn how important email is in a business setting, but we also learned how to setup and configure two different types of email servers, which are outgoing and incoming mail servers.

The Email Server Architecture

The Outgoing mail server uses SMTP. Simple mail transfer protocol is a server type used to receive emails from a different server. Although called, outgoing mail server, it’s also called the mail transfer agent. The Incoming mail server is how the mail is received by the client. The user can check the mail when they want because the message is stored in a local directory.

Sending Mail

Getting the message to outgoing mail server is done after the user is authenticated to send the message. The software called mail user agent (MUA) communicates with the outgoing mail server that I previously talked about. The SMTP protocol port that’s used is 25 or 587. Processing recipient’s address starts with the outgoing mail server examining the email sent. The email doesn’t go straight from sender to receiving. The message goes through many mail transfer agents (MTAs). Once it arrives it’s stored in a queue where the recipient can view it.

Receiving Mail

Receiving emails if much different than it used to be. Before everyone was online at every second, emails wouldn’t be received until the user logged on. Once they were online the email would be deleted from the server and be downloaded on the user’s computer. This outdated message was called the post office protocol (POP). POP3 is similar but more modern but still not as good as IMAP. The internet message access protocol syncs actions done to messages unlike POP/POP3. The drawback is that you need to be online to view all the emails. The more time that passes the less of an issue this is.

Configuring Sendmail Email Servers

Configuring the DNS MX record is the first step of configuring a Sendmail email server. Once the fields for the MX records are set (name, MX level, data, time to live) the Sendmail must be configured. One of the steps is to open the config file and change the DAEMON_OPTIONS line. This is so that it’s the actual mail server IP address. Configuring outgoing mail relays is important because the mail transfer agents and internet must forward the email, so it gets to the correct domain. We created virtual hosts for this week’s lab. This was done by using Vi (like all other configurations in this week’s lab) and overwriting /etc/mail/local-host-names. For normal accounts on a Linux server to receive mail they need an email account on the server.