What is an email server?

An email server is a computer program or a hardware device responsible for handling and delivering emails over a network, typically the internet. It acts as a virtual post office, managing the sending, receiving, and storing of email messages.

Here's how it works:

• Sending Emails: When you compose and send an email, your email client (such as Outlook, Apple Mail or Thunderbird) communicates with your email server to transmit the message. The email server then processes the outgoing message, including routing it to the recipient's email server.
• Receiving Emails: When someone sends you an email, their email server communicates with your email server to deliver the message. Your email server then stores the message until you retrieve it using your email client.
• Storage and Retrieval: Email servers typically include storage capabilities to store emails until they are retrieved by the recipient. Users can access their stored emails using email clients like Outlook, Apple Mail etc.

Email servers use various protocols such as SMTP (Simple Mail Transfer Protocol) for sending emails, and IMAP (Internet Message Access Protocol) or POP3 (Post Office Protocol) for receiving emails. SMTP is used to transmit emails between servers, while IMAP and POP3 are used by email clients to retrieve emails from the server.

Overall, email servers are essential components of the email infrastructure, facilitating communication and collaboration over the internet.

Opensource Components

MTA (Mail Transfer Agent):

• Postfix: Postfix is a widely-used MTA known for its security, flexibility, and performance. It is designed to be easy to configure and is a popular choice for setting up email servers.
• Exim: Another MTA that is commonly used in Unix-like operating systems. It is known for its flexibility and extensive feature set.

MDA (Mail Delivery Agent):

• Dovecot: Dovecot is a popular MDA that provides IMAP and POP3 services. It is known for its speed, security, and scalability. Dovecot can work seamlessly with Postfix or other MTAs.

MUA (Mail User Agent):

• Roundcube: Roundcube is a web-based email client that provides a user-friendly interface for accessing emails via a web browser. It supports features like rich text formatting, drag-and-drop, and multiple folder management.
• SquirrelMail: SquirrelMail is another web-based email client that is lightweight and easy to install. It is known for its simplicity and compatibility with various web servers and browsers.

Spam Filtering:

• SpamAssassin: SpamAssassin is a powerful and highly configurable spam filter that can be integrated with MTAs like Postfix to detect and filter spam emails based on various criteria such as header content, body content, and sender reputation.

Virus Scanning:

• ClamAV: ClamAV is an open-source antivirus engine that can be used to scan emails for viruses and malware. It can be integrated with MTAs like Postfix to provide real-time scanning of incoming and outgoing emails.