Mail server

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Revision as of 02:26, 8 July 2019 by Gary (talk | contribs) (General comparison)
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A mail server (hereinafter, the Server) is any digital construct that is located in a computer network under its distinguishable hostname in order to accept, analyze, adjust, clarify, and transfer electronic mail messages (or, simply, emails) from email clients to mail exchangers (MX hosts) and vice versa.

The Server can also refer to mail server software. More broadly, email software may refer to all the software utilized for email clients, the Servers, or mail exchangers.


Features

Protocols

To communicate with:
  1. Mail exchangers, all the Servers use the Simple Mail Transfer Protocol (SMTP).
  2. Email clients, the Servers use a variety of protocols, most commonly, POP3 and/or IMAP.

Functions

With regard to:
  • Outgoing messages, the Servers may be designed to:
    1. Accept messages from email clients.
    2. Analyze messages looking for their inconsistencies and/or missing data.
    3. Adjust messages while correcting inconsistencies and/or adding the missing data.
    4. Transfer messages to mail exchangers.
  • Incoming messages, the Servers may be designed to:
    1. Accept messages from mail exchangers.
    2. Analyze messages looking for their inconsistencies and/or missing data.
    3. Add information about the found inconsistencies and/or missing data to the messages. This information may further be used by email clients to combat spam.
    4. Transfer messages to email clients.

Hosting

To communicate with email clients and mail exchangers, the Servers shall be located between those two.
  1. Email clients are hosted at either:
    • End-user devices such as a mail app on a cell phone; or
    • Mail service provider such as Gmail locations.
  2. The Servers are hosted by local computing devices that are connected to the Internet. On the one side, they can be colocated with email clients, especially if the email client is hosted by a mail service provider. On another side, the Server can can colocated with mail exchangers when the mail service provider is an Internet service provider (ISP). Unix-based operating systems include the Server in their bundles, so do some end-user applications such as MediaWiki, Moodle, and Redmine. At the same time, the Servers can also be hosted separately from email clients and mail exchangers.
  3. Mail exchangers are hosted by Internet service providers (ISPs), who also run DNS resolvers, which provide mail exchangers with DNS records.

Agents

Best practices

Software

General comparison

General comparison of the popular Clients
Category Features Dovecot Kolab MS Exchange Postfix Sendmail
Legal properties Ownership OSS OSS Proprietary OSS OSS
Developer Community Community Community Foundation Corporation
License MITL, LGPLv2 Unknown GPL MPL YPL-like
Latest release 2.3.5 2019 (16) 1.2.5 60.7.2 8.6.0
History 3/5/2019 09/24/2018 04/28/2017 06/20/2019 12/15/2014
Introduction 2002 1997 2006 2003 2005
OS Windows No Yes Cross-platform Cross-platform Cross-platform
macOS No Yes
Linux UNIX-like No
BSD No
Unix No
Category Features Dovecot Kolab MS Exchange Postfix Sendmail