How email works

-

Using email is very easy, but setting up your own email server is not. This article describes how email works to give you an introduction on the various components needed to implement your own mail server.

  • The sender uses a Mail User Agent (MUA) to compose an email. An MUA, often referred to as a mail client, is a program that allows a user to compose, send and receive email.

  • The mail is sent to a Mail Transfer Agent (MTA) which is responsible for sending the email to the receipient’s MTA. An MTA transfers mail messages between computers via the SMTP protocol. Postfix, Sendmail, Exim and Qmail are examples of an MTA.

  • The recipient’s MTA receives the email and passes it on to a Mail Delivery Agent (MDA). An MDA manages the user’s mailbox and handles mails for delivery to the MUA using either the POP or IMAP protocol.

    • POP (Post Office Protocol)

      Although most mail clients have an option to Leave a copy on the server, POP is generally used to download all messages from the mailbox, store them on the user’s PC as new messages and delete them from the server.

    • IMAP (Internet Message Access Protocol)

      Allows users to view their mailboxes on the server and to delete mail only when told to do so.

    Mbox and Maildir are two common mailbox formats used in Unix. Dovecot, Cyrus and Courier are examples of an MDA.

  • The recipient uses an MUA to check and retrieve messages from the MDA.

Comments

Post a Comment

Popular posts from this blog

Some common php modules

-
I often use common php modules below: php-cli : Command-line interface for PHP php-common : Common files for PHP php-dba : A database abstraction layer module for PHP applications php-devel : Files needed for building PHP extensions php-embedded : PHP library for embedding in applications php-fpm : PHP FastCGI Process Manager php-gd : A module for PHP applications for using the gd graphics library php-imap : A module for PHP applications that use IMAP php-ldap : A module for PHP applications that use LDAP php-mbstring : A module for PHP applications which need multi-byte string handling php-mysql : A module for PHP applications that use MySQL databases php-odbc : A module for PHP applications that use ODBC databases php-pdo : A database access abstraction module for PHP applications php-pear.noarch : PHP Extension and Application Repository framework php-pecl-apc : APC caches and optimizes PHP intermediate code php-pecl-apc-devel : APC developer files (header) php-pecl...
Read more

Nginx web server with SSL

-
Some Web sites, such as on-line stores, require secure communication (HTTPS) to protect credit-card transactions and customer information. Like Apache, Nginx supports HTTPS via an SSL module, and it’s very easy to set up. In this tutorial i use hostname srv-web01.nginx.vn with the ip address 10.11.218.251. First, you need to generate an SSL certificate. The openssl command will ask you a bunch of questions, but you simply can press Enter for each one: # yum install openssl # mkdir /etc/nginx/ssl # cd /etc/nginx/ssl # openssl req -new -x509 -nodes -days 265 -newkey rsa:2048 -out server.crt -keyout server.key Create a new config file called /etc/nginx/sites-available/nginx.vn, which contains the following: server { listen 443; server_name nginx.vn; root /var/www/nginx.vn index index.html index.htm access_log /var/log/nginx/nginx.vn-access.log; error_log /var/log/nginx/nginx.vn-error.log; ssl on; ssl_certificate /etc/nginx/ssl/server.crt; ssl_certificate_key ...
Read more

Using nginx as http load balancer

-
Image
Load balancing across multiple application instances is a commonly used technique for optimizing resource utilization, maximizing throughput, reducing latency, and ensuring fault-tolerant configurations. Nginx is a very efficient HTTP load balancer to distribute traffic to several application servers and to improve performance, scalability and reliability of web applications. Nginx Load balancing methods The following load balancing mechanisms (or methods) are supported in nginx: round-robin least-connected ip-hash See detail at http://nginx.org/en/docs/http/load_balancing.html Initialization Nginx Load Banlancing In this tutorial I use any hostname and ip addresses as follows: srv-lb01 (10.11.218.250) (Nginx load balancer) srv-web01 (10.11.218.251) ( Web server) srv-web02 (10.11.218.252) ( Web server) srv-web03 (10.11.218.253) ( Web server) Note: pointing nginx.vn to 10.11.218.250 (Replace nginx.vn with your real site name) Default load balancing c...
Read more