A Guide to POP3 Server Installation

A Guide to POP3 Server Installation

A Guide to POP3 Server Installation


The Whys and Wherefores of Email and POP3 Server


What and Why is Email?

An email has become the absolute standard means of communication between individuals, teams, and organisations.  People may communicate using single or group messaging tools like Skype or WhatsApp, but email has replaced the letter as the de-facto standard for non-verbal communications.

The number of email users worldwide continues to grow. In 2017 there were nearly 270 billion emails sent every day.  In 2019, 294 billion, and by 2023, daily email volumes are estimated to reach 347 billion.

Businesses can choose to implement their own in-house domain mail server using a Windows platform like Exchange or its Linux equivalent.  Organisations who have outsourced their IT infrastructure can ask their MSP to host a domain email server on their behalf.   MSPs and ISPs can offer email hosting services as part of their service portfolio.  Other independent organisations act as email hosting service providers.

An email server essentially consists of two parts, a module to receive incoming emails, and a module to send outgoing emails. POP3  for incoming email, SMTP for outgoing.


What is a POP3 Server?

What is POP3 server?


Simply put, POP3 Server is a protocol standard for retrieving email from a remote server.

Incoming emails operate to the IMAP or POP3 standard.  IMAP is server-based, and POP3 is a client/server implementation The difference is that with IMAP, the reader interacts directly with the mail server, and with POP3, the emails, plus attachments are downloaded to the reader’s computer for reading later in an email client like Outlook.


Why POP3 Server?

The advantage of the POP3 Server is that you can work offline since you do not need to be connected to the mail server to read and process email, as you do with IMAP.   Emails you want to send are queued until you are online again.

However, having said that, it is possible to use IMAP in synchronous mode.  A copy of the emails held on the server are mirrored on the client computer, and a periodic synchronisation keeps them in step.

Many email server products include support for POP3 Server, for example, Gmail, (though they seem to discourage it), Exchange, and other Windows-based offerings.  Similar products exist for Linux and open-source installations.

There are proposals for POP4 Server, but only as an informal proposal and they seem to have stalled.

Setting POP3 Server up

Installing a POP3 server is a two-step process, setting up the server end to receive email and interact with the client mail application, and installing the client application itself.

Step One

The first step is to define the email domain.  This is usually the same as the organisation’s Internet domain name.

POP3 Server carries out some checks, for example, that Fred is a known user in the acme.com domain, or that the email is in an acceptable format, and that it doesn’t contravene any local usage rules.

In many organisations, emails are intercepted by anti-malware and content-checking software before it reaches the POP3 server. Anti-malware software scans the email and any attachments for malware, and content-checkers inspect the mail and any attachments to see they do not break local usage rules, for example, sent by a blocked sender or contains attachments that are executable files.


Step Two


Step two is a basic configuration.   There are two levels – server level and user level:


Server Level


The first and most important step is to make sure that you are not operating as an open server or mail relay.    Bulk email spammers continually scour the Internet for open servers and use them to relay their spam email.   The server must be configured to receive only the email addresses to the email domain, and only send emails from the email domain.

If your ISP or an email intermediary detects that you are sending high volumes of email, then your server might be blacklisted, losing your email service entirely. It is a difficult, lengthy and tedious process to remove your domain from a blacklist.

Other considerations include any server-level rules for directing mail.  Some organisations have collective addresses, for example,  emails sent to an address are forwarded to an individual mailbox for processing.   Using collective addresses means you can change the internal recipient without altering any other information.

Integration with anti-malware may also need attention.


User Level

If you are running a domain mailbox supporting many users, each user will need an email address, a mailbox allocated within the server, and an initial password to access the mailbox.   Users should be forced to change the password the first time they use the mailbox.


Things to Know and Remember

  • Make sure that the MX record for the server is properly set up in DNS
  • Use the correct user connection settings:
    1. Port 110 for an unencrypted connection, 995 for encrypted
    2. Setup the default security setting for connections. For instance, is SSL/TLS needed?
    3. Does user logon need SPA? You might need it if you have SSO in your organisation.
  • Set up policies and procedures for adding/modifying/deleting user mailboxes.
  • Users tend to forget passwords, so a policy for password management must be available.


Setting up a POP3 server is not difficult.

We at HostSailor have done it many times.  For help, guidance or just an informal chat, contact us

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