POP3 is the most up to date version of the Post Office Protocol, and it lets email applications retrieve email messages from email servers. This means that wherever you access a web-based email service you can get at your mail.

POP3 is one of several standard email retrieval protocols and its supported by the majority of email apps and web services. POP3 lets you access your emails so you can read them online or save them off-line, but one of its features is that your messages are deleted as soon as you’ve looked at them. POP3 can be made secure using an encrypted connection with STLS, TLS or SSL.

The POP3 protocol is simple and widely supported so it works with online services like Gmail and Hotmail and clients such as Thunderbird and Outlook

When you log in to access your email using POP3, you need to remember that your messages will be downloaded to whatever device you are using the time. So, once they’ve been deleted from the POP3 server, they will only exist on your device, most email clients you could set received messages to remain on the server for a longer period.

For sent messages, POP3 sends them but doesn’t save them to your local Sent email box. It typically uses the 110 port and the 995 port when the connection is encrypted.


Both the POP3 and IMAP protocols are widely supported for email retrieval. Of the two, IMAP is the newer and more adaptable one, and it’s usually the protocol of choice. IMAP leaves emails on the server automatically, so the user will always have them until they choose to delete them. This means you don’t need to fill your hard disk (or disks on different machines) with emails, and they are always safe and accessible. As long as you have a connection, a browser or a webmail client you can get at your email messages from anywhere.

This suits corporate or educational email accounts that need to be available to many people. Overall, IMAP has more options for managing emails, for the best of both worlds using IMAP and POP3 covers everything.


Postfix is a hugely-popular Mail Transfer Agent (MTA) designed to determine routes and send emails. This cross-platform server is open-source, free, and suitable for installation on the majority of UNIX-like operating systems.

Numerous client and server programs make up Postfix: the latter tend to run in the backend, while user or administrator programs utilize the former. Postfix’s structure is modular: it comprises various small, independent executables. Different parameters, features, and options are available, too.

Another key aspect of Postfix is that it was created to overcome those drawbacks seen in Sendmail. A solid configuration keeps Postfix user data secure from leakage, abuse, and spam.

Postfix includes a cutting-edge queue manager capable of handling queues in a faster, smoother way. That’s why a number of administrators cite Postfix’s higher efficiency compared to Sendmail, even with high loads.

With Postfix, you can expect a significant degree of flexibility and simple administration, which makes it easier for beginners to set up than alternative MTA options. On top of this, Postfix offers support for Sendmail’s command line interface. It’s also compatible with a variety of Sendmail’s mail filters.

Advantages of Postfix

Here are the main advantages you can expect to find when you start using Postfix:

  • Includes highly-detailed documentation
  • Security was clearly a priority in Postfix’s design
  • Postfix offers impressive compatibility with Sendmail
  • High queuing operation is fundamental to Postfix’s functionality
  • Active development is part of the Postfix set-up
  • Easy configuration, according to parameters of configuration files

Disadvantages of Postfix

  • Unfortunately, Postfix can be hard to customize in some cases, depending on your unique requirements

We hope this brief guide has helped you understand Postfix better, so you can make an informed choice!


qmail is a mail transfer agent ( MTA ) written in late 1995 by Daniel J. Bernstein. It was designed to run on UNIX and to serve as a replacement for Sendmail, albeit with higher security.

While this software was license-free when it launched, Bernstein later decided to make qmail’s source code public-domain material.

But what are qmail’s main advantages? Why should you consider using it as your MTA? Join us as we explore qmail’s top benefits below:

A tight focus on security

Security is paramount for any reliable mail transfer agent, and this was a primary concern for Bernstein when he authored qmail 25 years ago. As the original security-aware MTA, qmail broke new ground, inspiring the publication of many other MTAs with a focus on security-aware design since.

Sendmail, the most popular of qmail’s predecessors, lacked security as a core goal — which left it open to attack and exploitation. However, qmail is a stark contrast to Sendmail due to its modular architecture, which means it’s constructed from mutually-untrusting components. For example, qmail’s SMTP listener operates with credentials that vary from the SMTP sender or queue manager.

qmail was also released as a security-aware replacement for the C-standard library. This safeguarded it against the risks of stack and heap overflows, temporary file race conditions, or format string attacks.

qmail’s incredible security measures offer valuable peace of mind, which is crucial for any good MTA.

High performance

qmail was recognized as being considerably quicker than Sendmail upon its release, especially when handling bulk-mail actions (e.g. mailing list servers). That’s because it was initially created as a solution for mailing-list management on a large scale.

Streamlined simplicity

When qmail was launched, Sendmail’s configuration was well known for its complexity. But qmail made a refreshing change, as it was so easy to set up and deploy.

Breaking new ground

qmail is recognized for its mail innovations, but not all of them are the work of Bernstein. These groundbreaking elements include:


Bernstein created the Maildir format specifically for qmail. This is designed to separate emails into their own files, unlike the standard mbox format that keeps all messages within a single file.

Maildir sidesteps a number of locking and concurrency issues, and it can be equipped over NFS securely. qmail is also known for its ability to deliver to mbox mailboxes.

User-controlled wildcard mailboxes

User-controlled wildcards were introduced via qmail. Messages addressed to “user-wildcard” on qmail hosts are sent to separate mailboxes, which enables users to publish numerous addresses. This is ideal for managing spam and setting up mailing lists.

Additional protocols

qmail is also responsible for the QMTP (Quick Mail Transport Protocol) and QMQP (Quick Mail Queuing Protocol) protocols.


qmail is almost a totally modular system, with every key function separated from the others. As a result, it’s simple to replace any single part of the system with an alternative module — provided said replacement has an identical interface to the original one.

So, it’s clear that qmail offers a number of incredible advantages, not least high-end security and modularity. We hope this expert guide helps you to determine if this MTA is the right option for you and your mail!


RoundCube is a popular IMAP web-based email client, known for utilizing AJAX (Asynchronous JavaScript and XML) technology. This open-source, free software operates under the rules of the GNU GPL (General Public License), except for the plugins and skins.

RoundCube’s original stable version was announced to the world at the start of 2008, and it has built a wide user base since. But what about its core technology, plugins, and features?

The technology of RoundCube

RoundCube is PHP-based, capable of being utilized alongside a LAMP stack or other operating systems (provided they offer support for PHP). The web server requires access to the IMAP server that hosts the email, as well as an SMTP server, to ensure it’s capable of delivering messages.

RoundCube Webmail is built to function on such common web servers as LiteSpeed, Apache, Lighttpd, Nginx, Cherokee, or Hiawatha, along with a relational database engine. The following databases are supported: PostgreSQL, SQLite, and MySQL.

Furthermore, the UI (user interface) can be customized with a variety of skins for detailed personalization. It’s rendered in CSS and XHTML.

jQuery is incorporated into RoundCube for its distribution, in conjunction with a number of alternative libraries including TinyMCE and GoogieSpell.

RoundCube Plugins

Ever since RoundCube version 0.3 was launched, it has utilized a plugin API enabling users to introduce non-standard features without having to alter the source code. A number of plugins can be found in the Plugin Repository.

What was RoundCube Next?

Back in 2015, RoundCube revealed plans to partner with Kolab Systems AG and rewrite RoundCube completely — paving the way for RoundCube Next. A crowdfunding campaign was created to gather financing for the project, with incredible results: the project’s $80K goal had been achieved within two months, and the final sum was in excess of $100K.

RoundCube Next was originally conceived to incorporate such features as file management, a calendar, and chat. It would also use WebRTC and connectors from OwnCloud, Dropbox, and more.

Sadly, though, RoundCube and Kolab Systems chose to end RoundCube Next’s development in 2016.

RoundCube features

You can expect to find the following features in RoundCube:

  • More than 70 languages to choose from, making RoundCube accessible to a diverse audience
  • UI (user interface) incorporates AJAX technology, enabling users to take advantage of various convenient features; these include the ability to manage messages with simple drag-and-drop functionality
  • Can connect to all IMAPv4 servers
  • Total HTML and MIME message support
  • Encrypted TLSv1.2 connection to IMAP server via PHP5.6 SSL/TLS libraries
  • Privacy protection is of a high standard
  • Numerous sender identities
  • Create Rich Text/HTML messages and add attachments
  • Support for IDNA
  • Threaded message listing
  • Integration of LDAP directory, for address books
  • vCard with group support, for a full featured address book
  • Integration of find-as-you-type address book for extra convenience
  • In-built caching for quick access to the mailbox
  • Forward messages carrying attachments easily
  • Search contacts and messages
  • Check spelling for a higher standard of professionalism and presentation
  • External SMTP server support
  • IMAP folder management
  • Shared/global folders and IMAP ACLs can be supported
  • Widescreen (three columns) view for mailbox
  • Templates for canned responses
  • Custom theme templates

RoundCube is packed with amazing features, and its user-friendly design ensures it’s accessible to everyone, regardless of experience or technical knowledge.


Sendmail is a Mail Transfer Agent (MTA) designed for email routing, offering support for a variety of email transfer and delivery options. With Sendmail, Simple Mail Transfer Protocol ( SMTP ) is utilized for transporting messages across the Internet efficiently.

Another critical element of Sendmail is its monolithic design, which features a single process that runs at the backend at all times. But how about some of the benefits and drawbacks of using Sendmail as your MTA?

Advantages of Sendmail

Beginners should keep the following advantages in mind when trying to decide whether Sendmail is right for them or not:

  • Significant flexibility
  • Configuration is simple, even for inexperienced users
  • Impressive portability

Disadvantages of Sendmail

Fortunately, Sendmail offers more positives than negatives, but the following are still important. Think about these carefully before you make your decision:

  • Sendmail can be hard to customize
  • The security mechanism at Sendmail is considered less than adequate by some users

As you can see, there’s considerable incentive to sign up with Sendmail, but there are a couple of negative factors to think about too. Take the time to investigate it a little more deeply before committing.

We hope this look at Sendmail has helped to make its processes and functionality a little easier to understand!


SMTP stands for Simple Mail Transfer Protocol, an application layer protocol. The client who wants to send the mail opens a TCP connection to the SMTP server and sends the mail via this connection. The SMTP server is always on listening mode. As soon as it listens for a TCP connection from any client, the SMTP process initiates a connection on that port. After successfully establishing the TCP connection the client process sends the mail. The most common port for SMTP are 25,25 for sending out without encryption. 465 and 587 are used with SSL/TLS/STARTTLS.

To send and receive messages you need either an email client or a web-based mail service that uses the SMTP to send emails and POP3 or IMAP (preferably both) for receiving them. Most email providers use all the standards needed. You should also inquire if they offer secure email connections. If you want free email hosting for your site and you’d like to send emails to your users, check that your hosting provider gives free SMTP access.


A use of electronic messaging systems in order to send out unwanted messages in a bulk. To stop the SPAM is not a technical issue but mostly an economical one – the possible visibility in comparison to costs is still amazingly high.

The most popular spam type is e-mail SPAM, however the definition also applies to any messages sent electronically that are 100% unsolicited. The examples of SPAM are: search engine spam, comments spam, wiki spam, social media spam etc.

In majority of civilized countries SPAM is illegal. In the same time it is not so easy to catch the spammers since nowadays majority of SPAM campaigns are sent not from a single location, but from botnets, and they reside in different geo’s and networks.

SPAM filter

The name SPAM started life in 1937 as a brand of canned cooked pork that made it easy to deliver meat to soldiers on the front line. Unfortunately, these days you’ll notice is the name of the unwelcome emails that fill your inbox.

To fight SPAM, we have email SPAM filters. They are easy to set up, but your filtering software needs to be compatible with your email software and services, and flexible to meet your needs. The SPAM filter’s job is to find it and either deleted move it to your SPAM folder.

SpamAssassin is one of the most popular open-source email SPAM filters. It offers great flexibility and use a variety of techniques to detect and deal with SPAM. These include content-matching rules, using SPAM databases, text-analysis and Bayesian filtering. SpamAssassin is written in Perl, is highly configurable and easy to extend, so it’s easily possible to add more features. It’s compatible with most email platforms and is easy to set up.


Let’s take a look at SpamAssassin—the Swiss army knife of spam detection. Spam is unwanted or unsolicited email that is sometimes malicious. Spam filters were created to be one of the easiest ways of detecting and blocking this kind of unwelcome communication, and SpamAssassin is one of the most effective email spam filters.

SpamAssassin works with most systems. It was written in Perl and It can be customized using content-matching rules, spam databases, text analysis and Bayesian filtering. It’s very easy to extend and improve, because it’s constantly learning from the information you give to it. (You could say it feeds on spam, and spam makes it smarter!)

SpamAssassin adjusts its rules as it learns from the spam it receives, so it’s always working to keep itself up to date.

If you need it to block certain email accounts too, then it’s perfectly happy to do that. And why would you want to do that? Well, you might need to block someone who is problematic, or you might want to avoid receiving certain file formats.

So, every time you receive an email, SpamAssassin puts it through a number of tests.  It’s looking for various indicators, like certain words in the header or bad HTML in the message body. There are all kinds of things that suggest that the message could be spam, so it consults various spam databases to make most of its decisions. However, it’s also flexible enough to let you disable certain tests and roles or add new ones.

SPF Record

The open standard that checks to determine if your email address is valid is called SPF ( Sender Policy Framework ). The SPF record is one of the DNS records which stores information and regulates your domain names’ functions. The main use of SPF is to stop email SPAM, which mostly originates from forged addresses. SPF records are the ideal way to prove that an email did indeed come from your domain’s mail servers.

When an email goes out without a defined SPF it could have come from pretty much anywhere. That’s precisely the reason why most email systems won’t accept messages if they don’t come with an SPF record. They’ll either reject them or treat them as SPAM. Gmail, Hotmail, Yahoo, AOL and others require your SPF record and their networks won’t let you send email without one. So, it’s important to be sure that your email and web hosting services will let you set SPF records.

When your message goes to a mail server, it checks your DNS records for the SPF. If it finds one then it looks to see if the email came from the same server mentioned in the record. You can put an SPF in the TXT record to show which servers are allowed to send email messages from your domain. For example, when you send emails from [email protected] the SPF records should include mysuperdomain.com, which validates the domain.

You could also add more of your domains but be aware that the most SPF record checks that can be done is set at 10 DNS lookups. The functions used in SPF that require DNS lookups are “include”, “a”, “mx”, “ptr”, and “exists”, part of this list is the “redirect” modifier also.