Top 10 best mail server programs for VPS

In this article, we'll take a look at the most popular programs that can help secure email messages and protect against spam.

EXIM

A mail agent developed in 1995 for Linux-based servers. It is free and open source software distributed under the terms of the GNU license, which means that you can easily download the latest version and install it on your server. Among all free mail servers, Exim is almost universally regarded as the best, especially as far as antispam is concerned. It combines perfectly with WordPress and effectively monitors all applications that openly or covertly monitor the server.

Key features of the Exim agent:

• provides virtual domains, SMTP authentication;
• has awesome tools to protect against spam and viruses;
• supports current types of signatures and mail verification (SPF, DKIM, and DMARC);
• has a delivery filter;
• is designed with a flexible mail filtering concept based on access control lists - which means that the mail server can automatically handle incoming messages and outgoing correspondence.

However, this mailer also has disadvantages - poor optimization of mail queues and lack of delivery reporting mechanisms.

OPENDKIM

A difficult to configure but incredibly cool in practice mail server, which combines several efficient tools for phishing and spam filtering. This agent uses domain keys to identify emails and all outgoing emails are also digitally signed. Using the DomainKeys Identified Mail method significantly improves the quality of identifying legitimate mail arrivals and increases the efficiency of filtering mechanisms.

OPENDKIM's only drawback is its complexity. Only an experienced administrator can properly configure and organize the application.

OPENDMARC

An open-source mail service that also applies the DMARC (Domain-based Message Authentication, Reporting, and Conformance) method for filtering. This approach provides the highest level of domain protection against unauthorized access. BEC attacks, phishing emails, email scams, and other cyberthreat scenarios - DMARC is considered one of the most reliable email filters that have been developed as of this writing.

OPENDMARC software easily cuts out any intrusive ads and is capable of collecting detailed statistics about the senders of all incoming messages. Analytics and automatically collected reports allow the administrator to configure server security more effectively.

DOVECOT

A free IMAP and POP3 server with a strong emphasis on security and configuration flexibility. It is designed for UNIX-like operating systems. The main features of the Dovecot mail agent are:

• Supports popular mbox and Maildir formats;
• Consumes minimal system resources and is amazingly fast, thanks to the indexing of mailbox content;
• Multiple storage mechanisms are supported;
• It can be authenticated via SSL for security purposes;
• There are many plugins that somehow expand the functionality of the email client;
• IMAP compliance is claimed;
• Support for all current server operating systems: Linux, Solaris, FreeBSD, OpenBSD, NetBSD, and Mac OS X.

On top of that, you can set up access restrictions for each Dovecot user via the IMAP protocol and Access Control List. This application is very secure - its developer once promised $1,000 to anyone who would find at least one major remote vulnerability, but no one has managed to do so.

POSTFIX

Postfix software was developed by Wates Venema in 1999. The author set himself the task of creating a convenient and functional mail agent with a modular architecture so that anyone could assemble the best version for himself, like a construction set. As a result, Postfix has a UNIX-like architecture and consists of many small programs which perform various functions. They are very simple, consume minimal resources, and work on behalf of unprivileged users, thus achieving higher security. The capabilities of this mail agent are quite extensive:

• Supports an unlimited number of domains and users;
• Can serve users without a local account;
• Guarantees mailbox access using POP3.

Compared to the older Sendmail agent, Postfix has a simpler, more elegant configuration, consumes fewer resources, and is resilient. In fact, it can be built and ready to run on any UNIX-like system with a C compiler. Because of its many advantages and simplicity, it is even used by default on NetBSD for correspondence management.

POSTFIXADMIN

This is a web interface that greatly simplifies the tasks of Postfix mailbox administration and management. In particular, it allows you to:

• change passwords;
• assign and deprive administrators of their rights;
• add and delete domains, mailboxes, aliases.

You can store the settings from the software in a MySQL or MariaDB database. You can also use this web interface in conjunction with iRedMail, an off-the-shelf Postfix-based build.

CLAMSMTP

It is not a standalone full-fledged mail server, but it is a very good filter that checks all incoming mail for viruses. A simple and reliable program that does not depend on libraries. Usually it is used together with ClamAV + clamsmtpd + Postfix under Linux. Virus threats filtering and detection is the task of the ClamAV anti-virus distributed under the GPL license.

It will take some time to get up and running but it's well worth it because ClamAV performs even better than Microsoft Security Essentials. It effectively protects gateways, provides real-time traffic scanning, and consumes very few server resources. It's a solid option to use as your first line of defense.

SPAMASSASSIN

This software is an email filter based on three key components:

• Evaluation Service.
• Transport agent.
• A database of email templates.

SpamAssassin uses Bayesian filtering and a number of other spam detection methods during its operation: DNSBL, Sender Policy Framework, DomainKeys, DKIM, and Razor. This tool is often used to filter the words and phrases most often found in malicious newsletters. This tool can be used in conjunction with the Postfix or any other mail service to block unwanted mails.

CERTBOT

Certbot is an ACME client that automates the management of SSL certificates issued by Let's Encrypt. With Certbot you can automate the procedure of obtaining and renewing SSL certificates, which in practice is very important for security.

The second important function of this software is the automatic configuration of Apache and Nginx web servers.

ROUNDCUBE

Mail client with a simple and clear interface that allows you to:

• create mail messages;
• work in the address book;
• to identify the sender;
• to check photos.

The client supports emails in IME / HTML formats. It can be installed on almost any web server that supports PHP version 5.4.0 and above. It can work in conjunction with MySQL, PostgreSQL, SQLite, MSSQL or Oracle Database.

SQUIRRELMAIL

A module that supports IMAP and SMTP protocols, this client has its own web interface written in PHP. SquirrelMail functionality:

• creation of logs;
• there is a calendar;
• mail encryption with GnuPG;
• spam filtering.

Compatible with most modern browsers, and has a number of additional plugins that can be installed to extend the standard functions. For example, you can use the avelsieve plugin to work with Sieve-filters on the server, and Empty Folders is good for cleaning up entire mail folders.

Here we conclude our review of popular mail servers and related software. If you need to order a VPS with pre-installed mail services, contact HostZealot - we’ll help you get started.