James - Enterprise Mail Server

•    Java

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James (a.k.a Java Apache Mail Enterprise Server) is a 100% pure Java SMTP and POP3 Mail server, and NNTP News server designed to be a complete and portable enterprise mail/messaging engine solution based on currently available open messaging protocols.

mail-server email-server enterprise mailing-list smtp lmtp pop3 nntp imap mta mail-delivery-agent

ZoneMTA - Modern outbound MTA cross platform and extendable server application

•    Javascript

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ZoneMTA is a modern outbound MTA cross platform and extendable server application. Modern outbound SMTP relay (MTA/MSA) built on Node.js and MongoDB (queue storage). It's kind of like Postfix for outbound but is able to use multiple local IP addresses and is easily extendable using plugins that are way more flexible than milters.

mail-server mta mail-transfer-agent smtp smtp-relay smtp-server

Haraka - A fast, highly extensible, and event driven SMTP server

•    Javascript

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Haraka is a highly scalable node.js email server with a modular plugin architecture. Haraka can serve thousands of concurrent connections and deliver thousands of messages per second. Haraka and plugins are written in asynchronous JS and are very fast. Haraka has very good spam protection (see plugins) and works well as a filtering MTA. It also works well as a MSA running on port 587 with auth and dkim_sign plugins enabled.

smtp mta spf dkim email mail-server smtp-server mail-transfer-agent smtp-relay

Exim - Message Transfer Agent

•    C

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Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet. There is a great deal of flexibility in the way mail can be routed, and there are extensive facilities for checking incoming mail.

smtp mta message-transfer-agent email-server mail-server

Maddy - Composable all-in-one mail server

•    Go

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Maddy Mail Server implements all functionality required to run a e-mail server. It can send messages via SMTP (works as MTA), accept messages via SMTP (works as MX) and store messages while providing access to them via IMAP. In addition to that it implements auxiliary protocols that are mandatory to keep email reasonably secure (DKIM, SPF, DMARC, DANE, MTA-STS). It replaces Postfix, Dovecot, OpenDKIM, OpenSPF, OpenDMARC and more with one daemon with uniform configuration and minimal maintenance cost.

mail-server email-server smtp-server mail imap smtp spf dkim dmarc

Docker Mailserver - A fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.) using Docker.

•    Shell

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A fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.). Only configuration files, no SQL database. Keep it simple and versioned. Easy to deploy and upgrade.

letsencrypt docker ssl ldap mail postfix imap smtp dovecot spamassassin antivirus fail2ban antispam mailserver opendkim amavis postgrey opendmarc docker-mailserver saslauthd-ldap smtp-server email-server mail-server

Citadel

•    C

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Citadel is a collaboration suite (messaging and groupware). It provides support for Email, Calendaring/Scheduling, Address books, Bulletin boards, Mailing List Server, Instant Messaging, Wiki, Multiple domain support.

mail-server groupware bulletin-board mailing-list wiki instant-messaging smtp pop3

amavisd-new - interface between mailer (MTA) and content checkers

•    Perl

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amavisd-new is a high-performance interface between mailer (MTA) and content checkers amd virus scanners. It talks to MTA via (E)SMTP or LMTP or by using helper programs. It works best with Postfix, Sendmail and Exim v4, works with sendmail/milter, or with any MTA as a SMTP relay. The content received from the mail server is processed with Spam and Anti virus scanner and based on the results the mails will be quarantined.

content-filter interface mail-filter mail

Courier Mail Server

•    C

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The Courier mail transfer agent (MTA) is an integrated mail/groupware server based on open commodity protocols such as ESMTP, IMAP, POP3, LDAP, SSL, and HTTP. Courier provides ESMTP, IMAP, POP3, Webmail, calendaring, and mailing list services.

fetchmail - TLS-enabled mail retrieval and forwarding agent

•    C

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Fetchmail is a full-featured, robust, well-documented remote-mail retrieval and forwarding utility intended to be used over on-demand TCP/IP links (such as SLIP or PPP connections). It supports every remote-mail protocol now in use on the Internet: POP2, POP3, RPOP, APOP, KPOP, all flavors of IMAP, ETRN, and ODMR. It can even support IPv6 and IPSEC.

mail-client mail retrieval mail-forward relay command-line email smtp pop3 imap

Claws Mail - Email Client and News Reader Based on GTK+

•    C

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Claws Mail is a GTK+ based, lightweight, and fast e-mail client and newsreader. Supports POP3, APOP, IMAP, SMTP, SMTP AUTH, NNTP, LDAP, multiple accounts, spell-checking, addressbook, SSL, GPG, filtering, i18n, & more. It is further extended by plugins. Lots of extra functionality, like an RSS aggregator, calendar, or laptop LED handling, are provided by extra plugins.

mail-client email-client mail pop3 smtp client newsreader rss-aggregator

Sylpheed - Lightweight and user-friendly e-mail client

•    GTK

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Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client. It provides intuitive user-interface, Powerful filtering and search, Junk mail control, Security features (GnuPG, SSL/TLSv1). Sylpheed supports not only the major protocols such as POP3, IMAP4rev1 and SMTP, but also NNTP (NetNews). IPv6, which is the next-generation Internet protocol, is also supported by default.

mail-client email-client mail pop3 smtp client

Postal - A fully featured open source mail delivery platform for incoming & outgoing e-mail

•    Ruby

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Postal is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready for you to run on your own servers. Postal was developed by aTech Media to serve its own mail processing requirements and we have since decided that it should be released as an open source project for the community.

mail smtp postal mail-server email-server mail-delivery-agent dkim mail-transfer-agent

WildDuck Mail Server - Self hosted modern mail server `

•    Javascript

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WildDuck is a modern mail server software for IMAP and POP3. Modern being scalable, unicode-first and API-controlled. You can bundle WildDuck with Haraka and ZoneMTA to create a complete mail server. It uses a distributed database (sharded + replicated MongoDB) as a backend for storing all data, including emails. It tries to follow Gmail in product design. If there's a decision to be made then usually the answer is to do whatever Gmail has done.

mail-server email-server pop3 imap docker smtp-server smtp imap-server pop3-server self-hosted

YPOPs! - POP3/SMTP Access to Yahoo

•    C++

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YPOPs! is an application which emulates a POP3/SMTP mail server and provides free POP3 and SMTP access to Yahoo! Mail. It does not depend on Yahoo's POP3/SMTP mail server. You can use a mail client of your choice!

hMailServer - E-Mail Server for Microsoft Windows.

•    C++

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hMailServer is an open source email server for Microsoft Windows. It supports the common e-mail protocols (IMAP, SMTP and POP3) and can easily be integrated with many existing web mail systems. It has flexible score-based spam protection and can attach to your virus scanner to scan all incoming and outgoing email.

email-server mail-server smtp-server imap pop3

CRSMail - JAVA based E-Mail server

•    Java

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CRSMail a 100% JAVA based E-Mail server. It supports SMTP, POP3, Plugins, Can listen on multiple ports, Log's everything to a log file etc.

smtp-server smtp pop3 mail-server email-server email

deepOfix - Mail Server

•    C

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The deepOfix Mail Server makes it possible for organisations with minimal technical expertise to have robust messaging infrastructure. It has built in LDAP support, SMTP, POP3 and IMAP services.

mail mail-server smtp pop3

Mailu - Mail server as a set of Docker images

•    Python

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Mailu is a simple yet full-featured mail server as a set of Docker images. The project aims at providing people with an easily setup, easily maintained and full-featured mail server while not shipping proprietary software nor unrelated features often found in popular groupware.

docker email imap pop3 webmail mailserver mail smtp docker-compose dkim dmarc fetchmail letsencrypt email-server mail-server self-hosted ldap

FedMail Mail Transfer Agent

•    C++

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Modular EMail Server with features to support SMTP-after-POP,Anti-Virus filter by using popular AV-Scanners,IMAP,POP3,SSL,ODMR,SASL and has an easy configuration. (SMTP,ODMR,IMAP,POP3,SASL,CHUNKING,BINARYMIME,PAM)