SMTP Server

SMTP Server (Exim) is an open-source Mail Transfer Agent (MTA) used to send, receive, relay, and route email messages between mail servers and email clients. It is designed to provide secure, reliable, and flexible email delivery for websites, applications, monitoring systems, and enterprise environments. Exim is widely used on Linux and Unix-based servers due to its powerful routing engine, extensive configuration options, and high scalability.

Features of SMTP Server (Exim):

• Reliable email delivery for applications, websites, and system notifications.
• Supports secure email transmission using SSL/TLS encryption.
• Provides SMTP authentication (SASL) to prevent unauthorized mail relay.
• Supports virtual domains, aliases, forwarding, and custom mail routing rules.
• Includes built-in support for spam prevention, access controls, and message filtering.
• Compatible with POP3 and IMAP servers such as Dovecot and Courier.
• Offers detailed logging, queue management, and monitoring capabilities.
• Highly configurable and suitable for cloud, virtual, and on-premises deployments.
• Can be integrated with SpamAssassin, ClamAV, DKIM, SPF, and DMARC.

To check the version of the SMTP Server (Exim), run the following commands:

$ sudo su
$ exim -bV

# Service Management
$ systemctl restart exim4
$ systemctl status exim4

# Check SMTP Port
$ ss -tulpn | grep :25

# Check Mail Queue
$ exim -bp

# Send Test Email
$ echo "SMTP Test Mail" | mail -s "Test Message" admin@example.com

Disclaimer:

Exim is provided "as is" under its applicable open-source license. Users are responsible for properly configuring hostname, DNS records (MX, SPF, DKIM, and DMARC), TLS certificates, authentication, firewall rules, and relay restrictions to ensure secure and reliable email delivery. Incorrect configuration may result in email delivery failures, open relay vulnerabilities, spam abuse, or security risks. It is recommended to follow security best practices and official Exim documentation before deploying an SMTP server in production environments.