The comparison of mail servers covers mail transfer agents (MTAs), mail delivery agents, and other computer software that provide e-mail services.
Unix-based mail servers are built using a number of components because a Unix-style environment is, by default, a toolbox [1] operating system. A stock Unix-like server already has internal mail; more traditional ones also come with a full MTA already part of the standard installation. To allow the server to send external emails, an MTA such as Sendmail, Postfix, or Exim is required. Mail is read either through direct access (shell login) or mailbox protocols like POP and IMAP. Unix-based MTA software largely acts to enhance or replace the respective system's native MTA.
Microsoft Windows servers do not natively implement e-mail, thus Windows-based MTAs have to supply all the necessary aspects of e-mail-related functionality.
OS support | Protocol support | Features | Storage | License | ||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mail server | Linux/Unix | Windows | macOS | SMTP | POP3 | IMAP | JMAP | IDLE | SMTPS | POP3S | IPv6 | SSL | DANE | Webmail | ActiveSync | Sieve | IDN/UTF8 | Database | File-based | |
agorum core | Yes | Yes | No | Yes | No | Yes | No | No | No | No | No | Yes | No | Yes | No | No | ? | Yes | No | GPLv2 |
Apache James | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | ? | No | No | Yes | ? | Yes | Yes | ASLv2 |
Axigen | Yes | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | ? | Ajax, Basic & Mobile | Yes | Yes | Yes | Embedded, Optimized for Email & Groupware | Yes | Proprietary (free version: 5 domains, 5 users, 5 groups) |
Citadel | Yes | No | Yes | Yes | Yes | Yes | ? | No | Yes | Yes | Yes | Yes | ? | Yes | No | Yes | ? | Yes | No | GPLv3 |
CommuniGate Pro | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | ? | Yes | Yes | Yes | Proprietary (Free for up to 5 users) |
Courier Mail Server | Yes | No | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | No | Yes | No | maildrop | Yes | No | maildir | GPLv3+ [2] |
Cyrus IMAP | Yes | No | Yes | No | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | No | No | No | Yes | No [3] | Indexes only | Yes | BSD 4-clause [4] |
DBMail | Yes | No | Yes | No | Yes | Yes | No | Yes | No | Yes | Yes | Yes | No | No | No | No | Yes | Yes | No | GPLv2 |
Dovecot | Yes [5] | No | Yes | Yes [6] | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | No | No | No | Yes | No | Yes | maildir, mbox, dbox, mdbox, obox [7] | Mixed: MIT and LGPL-2.1 [8] |
Eudora Internet Mail Server | No | No | Yes | Yes | Yes | Yes | ? | ? | No | No | ? | No | ? | No | No | ? | ? | No | No | Proprietary |
Exim | Yes | Yes (via Cygwin) | Yes | Yes | No | No | ? | No | Yes | No | Yes | Yes | Yes [9] | No | No | Yes | Yes | Yes | Yes | GPLv2+ [10] |
FirstClass | Yes | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | ? | Yes | ? | Yes | Yes | ? | ? | Yes | Yes | Proprietary |
Gordano Messaging Suite | Yes | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | ? | Yes | ? | Yes | Yes | No | ? | Yes | Yes | Proprietary |
GroupWise | Yes | Yes | No | Yes | Yes | Yes | ? | ? | Yes | Yes | ? | Yes | ? | Yes | Yes | ? | ? | Yes | No | Proprietary |
Halon | Yes | No | No | Yes | No | No | ? | No | Yes | No | Yes | Yes | Yes [11] | No | No | ? | Yes | Yes | Yes | Proprietary |
Haraka | Yes | Yes | Yes | Yes | No | No | ? | No | Yes | No | Yes | Yes | ? | No | No | ? | Yes | Yes | Yes | MIT |
hMailServer | No | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | ? | Yes | No | ? | No | Yes | Yes | GNU AGPL |
HCL Domino | Yes | Yes | No | Yes | Yes | Yes | No | No | Yes | Yes | Yes | Yes | No | Yes | Yes [12] | No | Yes | Yes | No | Proprietary |
IceWarp Mail Server | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | No | ? | Yes | Yes | Proprietary |
Ipswitch IMail Server | No | Yes | No | Yes | Yes | Yes | ? | Yes (since v12.2) [13] | Yes | Yes | ? | Yes | ? | Yes | Yes | ? | ? | No | Yes | Proprietary |
Kerio Connect | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | ? | No | Yes | Proprietary |
Kolab | Yes | No | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Yes | GPLv3 |
Kopano | Yes | No | No | postfix, etc. [14] | Yes | Yes | No | Yes | postfix | Yes | Yes | Yes | postfix | Yes | z-push | No | Yes | SQL | Yes | AGPLv3, paid [15] |
KumoMTA | Yes | No | No | Yes | No | No | ? | No | Yes | No | Yes | Yes | Yes | No | No | Lua | Yes | Yes | Yes | ASLv2 |
Mailsite | No | Yes | No | Yes | Yes | Yes | ? | ? | Yes | Yes | ? | Yes | ? | Yes | Yes | Yes | ? | Yes | Yes | Proprietary |
Mailtraq | No | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | ? | Yes | ? | Yes | No | ? | ? | Yes | Yes | Proprietary |
MDaemon | No | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | No | Not IMAP | No | Yes | Proprietary |
Mercury Mail Transport System | No | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | No | Yes | No | Yes | No | No | No | No | Yes | Proprietary donationware |
Microsoft Exchange Server | No | Yes | No | Yes | Yes | Yes | No | Yes [16] [17] | Yes | Yes | Yes [18] | Yes | No | Yes | Yes | 3rd Party support | Not IMAP | Yes | Yes | Proprietary |
NetMail | Yes | Yes | No | Yes | Yes | Yes | ? | ? | Yes | Yes | ? | Yes | ? | Yes | No | ? | ? | Yes | No | Proprietary |
OpenSMTPD | Yes | No | Yes | Yes | No | No | No | No | Yes | No | Yes | Yes | No [19] | No | No | No | No | via custom backends | Yes | ISC |
Open-Xchange | Yes | No | No | Yes | Yes | Yes | ? | ? | Yes | Yes | ? | Yes | ? | Yes | Yes | ? | ? | Yes | No | Proprietary/SaaS, with open-source parts [20] |
Oracle Communications Messaging Server | Yes | No | No | Yes | Yes | Yes | ? | ? | Yes | Yes | ? | Yes | ? | Yes | No | ? | Yes | Yes | Yes | Proprietary |
Postfix | Yes | No | Yes | Yes | No | No | ? | No | Yes | No | Yes | Yes | Yes | No | No | No | Yes | Yes | Yes | IBM Public License |
qmail | Yes | No | Yes | Yes | Yes | No | ? | No | No | No | via Qsmtp | No | No | No | No | ? | ? | (cdb) | Yes | Public domain |
Qpopper | Yes | Yes (via Cygwin) | Yes | No | Yes | No | ? | No | No | Yes | ? | Yes | ? | No | No | ? | ? | No | Yes | BSD-style (GPL-incompatible) [21] |
Scalix | Yes | No | No | Yes | Yes | Yes | ? | Yes | Yes (via Stunnel) | Yes (via Stunnel) | ? | Yes (via Stunnel) | ? | Yes | Yes | ? | ? | Yes | Yes | Proprietary with OSS parts, a community (Freeware) and 3 paid editions (SMB, Enterprise, Hosting) |
Sendmail | Yes | No | Yes | Yes | No | No | ? | No | Yes | No | Yes | Yes | Yes (since 8.16) [22] | No | No | No | Yes | ? | Yes | Sendmail License |
SparkEngine | Yes | Yes | Yes | Yes | No | No | ? | No | Yes | No | ? | Yes | ? | No | No | ? | ? | Yes | Yes | Proprietary |
UW IMAP | Yes | Yes | Yes | No | Yes | Yes | ? | Yes | No | Yes | Yes | Yes | No | WebPine | No | No | ? | Yes (Indexes) | Yes | Apache License 2.0 [23] |
WinGate | No | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | No | Yes | ? | Yes | No | ? | ? | No | Yes | Proprietary |
Zarafa | Yes | No | No | postfix etc. [14] | Yes | Yes | No | Yes | postfix | Yes | Yes | Yes | postfix | Yes | z-push | No | No | SQL | Yes | AGPLv3, paid [15] |
Zentyal | Yes | No | No | Yes | Yes | Yes | ? | Yes | Yes | Yes | No | Yes | ? | Yes | Yes | ? | ? | Yes | Yes | Proprietary, 45-day trial |
Zimbra | Yes | No | Yes | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | ZPL and proprietary editions [24] |
Mail server | Linux/Unix | Windows | macOS | SMTP | POP3 | IMAP | JMAP | IDLE | SMTPS | POP3S | IPv6 | SSL | DANE | Webmail | ActiveSync | Sieve | IDN/UTF8 | Database | File-based | License |
Mail server | SMTP AUTH | POP before SMTP | APOP | File System | Database | LDAP | Native Anti Hammer - Brute-force attack protection | Other |
---|---|---|---|---|---|---|---|---|
agorum core | Yes | No | No | No | Yes | Yes | ? | PLAIN, LOGIN, CRAM-MD5, [25] NTLM |
Apache James | Yes | ? | ? | ? | Yes | Yes | ? | PLAIN, LOGIN |
Axigen | Yes | No | Yes | Yes | No | Yes | No | GSSAPI, CRAM-MD5, [25] DIGEST-MD5, [26] APOP, CLRTXT, LOGIN, PLAIN, LDAP, Internal |
CommuniGate Pro | Yes | Yes | Yes | Yes | Yes | Yes | ? | Active Directory (LDAP), CLRTXT, CRAM-MD5, [25] DIGEST-MD5, [26] APOP, GSSAPI, NTLM, MSN, SESSIONID, External Authentication Plug-in. Also supports X.509 PKI auth via STARTTLS/SSL |
Courier Mail Server | Yes | Yes | Yes | Yes | Yes | Yes | ? | Managed by Courier authentication library which can use PAM, Userdb, PostgreSQL(beta), MySQL, LDAP, and EXTERNAL. |
Cyrus IMAP | Yes | Yes | Yes | Yes | Yes | Yes | ? | Supports X.509 PKI auth via STARTTLS and EXTERNAL. Uses Cyrus SASL authentication library for support for other mechanisms: Berkeley DB, GDBM, or NDBM (sasldb), PAM, MySQL, PostgreSQL, SQLite, LDAP, Active Directory(LDAP), DCE, Kerberos 4 and 5, proxied IMAP auth, getpwent, shadow, SIA, Courier Authdaemon, httpform, APOP and SASL mechanisms: ANONYMOUS, CRAM-MD5, [25] DIGEST-MD5, [26] SCRAM-SHA-1(-PLUS), SCRAM-SHA-224(-PLUS), SCRAM-SHA-256(-PLUS), SCRAM-SHA-384(-PLUS), SCRAM-SHA-512(-PLUS), EXTERNAL, GSSAPI, LOGIN, NTLM, OTP, PASSDSS, PLAIN, SRP |
DBMail | No | No | No | No | Yes | Yes | No | LOGIN, Active Directory, OpenLDAP |
Dovecot | Yes | Yes | Yes | Yes | Yes | Yes | ? | Submission service supports SMTP AUTH. [6] Offers SASL to MTAs. [27] [28] POP-before-SMTP via DRAC plugin. PAM, MySQL, PostgreSQL, SQLite, LDAP, Active Directory(LDAP), Kerberos 5, proxied IMAP auth, getpwent, shadow, SIA, BSDauth, Vpopmail. APOP and SASL mechanisms: ANONYMOUS, PLAIN, LOGIN, CRAM-MD5, [25] DIGEST-MD5, [26] SCRAM-SHA-1, EXTERNAL, GSSAPI, NTLM, OTP, SKEY, RPA. |
Eudora Internet Mail Server | Yes | No | Yes | Yes | No | No | Yes | CRAM-MD5, [25] DIGEST-MD5, [26] PLAIN, LOGIN |
Exim | Yes | Yes | Yes | Yes | Yes | Yes | ? | Cyrus SASL, Dovecot SASL, GNU SASL, CRAM-MD5, [25] Heimdal GSSAPI, PLAIN, LOGIN, SPA |
FirstClass | Yes | ? | ? | Yes | Yes | Yes | ? | |
Gordano Messaging Suite | Yes | Yes | Yes | No | Yes | Yes | ? | PLAIN, LOGIN, CRAM-MD5, [25] DIGEST-MD5, [26] APOP, ODBC, Active Directory, NT Domain |
GroupWise | Yes | Yes | Yes | Yes | Yes | Yes | ? | eDirectory, Any LDAPv3-compliant source |
Halon | Yes | No | No | Yes | Yes | Yes | ? | Many mechanism (SMTP callout, Dovecot SASL, REST, etc.) via script. [29] |
Haraka | Yes | No | No | Yes | Yes | Yes | ? | Proxy to other server, any other mechanism via AUTH plugins. |
IceWarp Mail Server | Yes | Yes | Yes | Yes | Yes | Yes | ? | PLAIN, LOGIN, CRAM-MD5, [25] NTLM |
Ipswitch IMail Server | Yes | No | Yes | Yes | Yes | Yes | Yes | Active Directory, Windows authentication, CRAM-MD5, [25] PLAIN, LOGIN |
Kolab | Yes | Yes | Yes | Yes | Yes | Yes | ? | Kolab employs Cyrus and Postfix and thus supports all Cyrus SASL authentication methods and X.509 PKI auth via STARTTLS and EXTERNAL. |
Mailsite | Yes | No | Yes | Yes | Yes | Yes | ? | NT Domain, Active Directory, PLAIN, LOGIN, NTLM, SCRAM-MD5, CRAM-MD5 [25] |
Mailtraq | Yes | Yes | Yes | Yes | Yes | Yes | ? | NT Domain, Active Directory, Local Directory |
MDaemon | Yes | No | Yes | No | No | Yes | Yes | |
Mercury Mail Transport System | Yes | Yes | Yes | Yes | No | ? | ? | Internal, LOGIN, PLAIN, CRAM-MD5, [25] Netware, LDAP?, partial NT Domain |
Microsoft Exchange Server | Yes | ? | Yes | No | No | Yes | Yes | Active Directory, LOGIN, [30] NTLM |
NetMail | Yes | Yes | Yes | Yes | Yes | Yes | ? | eDirectory, LDAP |
Oracle Communications Messaging Server | Yes | Yes | Yes | Yes | Yes | Yes | ? | Plain, Login, CRAM-MD5, [25] DIGEST-MD5, [26] Certificate |
OpenSMTPD | Yes | No | No | Yes | Yes | Yes | No | By default PLAIN and LOGIN over SSL only, Certificates, bsd_auth and PAM. Supports adding new authentication mechanisms through custom backends. |
Postfix | Yes | No | No | Yes | Yes | Yes | Yes | Supports all Cyrus SASL authentication methods except for APOP. |
Qpopper | No | Yes | Yes | Yes | Yes | Yes | ? | Pluggable Authentication Modules, GSSAPI, CRAM-MD5, [25] DIGEST-MD5, [26] APOP, PLAIN, LDAP, CMU SASL library, Kerberos |
qmail | with patch | with vpopmail | Yes | Yes | Yes | Yes | ? | Works with any checkpassword utility. The original supports only LOGIN and PLAIN. Alternate checkpassword utilities support authentication against PAM, LDAP, and databases. |
Scalix | Yes | ? | Yes | Yes | Yes | Yes | ? | Internal, LOGIN, PLAIN, X.500 (DAP), LDAP, OpenLDAP, Active Directory, eDirectory, Kerberos, etc. |
Sendmail | Yes | Yes | No | Yes | Yes | Yes | ? | Supports all Cyrus SASL authentication methods except for APOP. Also supports X.509 PKI auth via STARTTLS and EXTERNAL. |
WinGate | Yes | Yes | Yes | Yes | Yes | No | ? | NT Domain, Active Directory, CRAM-MD5, [25] SASL PLAIN, SASL LOGIN |
Zarafa | Yes | No | No | Yes | Yes | Yes | ? | PLAIN, LOGIN using internal backends: Internal, Active Directory, any LDAP-compatible source, Unix |
Zentyal | Yes | Yes | Yes | Yes | Yes | Yes | ? | Active Directory using Dovecot SASL mechanisms |
Zimbra | Yes | No | Yes | Yes | Yes | Yes | ? | Internal, LDAP, Open LDAP, Active Directory |
Mail server | SMTP AUTH | POP before SMTP | APOP | File System | Database | LDAP | Native Anti Hammer - Brute-force attack protection | Other |
Mail Server | DNSBL | SURBL | Spamtraps | Greylisting | SPF | DKIM | DMARC | Tarpit | Bayesian filters | Regular expressions | Embedded Antivirus | Embedded Antispam |
---|---|---|---|---|---|---|---|---|---|---|---|---|
agorum core | No | No | No | No | No | No | No | No | No | Yes | No | No |
Apache James | ? | ? | ? | ? | ? | ? | ? | ? | Yes | ? | Yes ClamAV [31] | Optional (Apache SpamAssassin) |
Axigen | Yes | No | Yes | Yes | Yes | Yes | ? | No | Yes, in SpamAssassin | Yes | Yes CYREN | Yes CYREN |
Citadel | Yes | Yes | No | No | Optional (via SpamAssassin) | ? | ? | No | Optional (via SpamAssassin) | No | Optional (ClamAV) | Optional (SpamAssassin) |
Courier Mail Server | Yes | ? | Yes | Yes [32] | Yes | Optional [33] | Optional [34] | Yes | Yes [32] | Yes [32] | Yes Clamav | Yes [32] |
Dovecot | No [35] | No | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Eudora Internet Mail Server | Yes | ? | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? |
Exim | Yes | Yes | Yes | Yes | Optional (at build time, most distributions do) | Optional (at build time, most distributions do) | Optional (at build time, most distributions do) | Yes | Optional with spamassassin etc. | Yes | Optional any | Optional any |
FirstClass | Yes | Yes | No | ? | Yes | ? | ? | Yes | Yes | Yes | Yes Symantec | ? |
Gordano Messaging Suite | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | Yes CYREN, Authentium | Yes CYREN |
GroupWise | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Halon | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Optional (via SpamAssassin) | Yes | Optional (Sophos, ClamAV) | Optional (CYREN, SpamAssassin) |
Haraka | Yes | Yes | Yes | Yes | Yes | Yes | ? | Yes | Optional with spamassassin etc. | Yes | Optional ClamAV, AVG, any via plugins | Optional SpamAssassin, MessageSniffer |
hMailServer | Yes | Yes | No | Yes | Yes | Yes | ? | No | No | Yes | Yes ClamAV | Yes SpamAssassin |
IBM Notes | Yes [36] | ? | ? | ? | No [37] | ? | ? | ? | ? | ? | ? | ? |
IceWarp Mail Server | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | Yes | Yes |
Ipswitch IMail Server | Yes | Yes | No | No | Yes | Yes [38] | Yes [39] | No | Yes | Yes | Yes Symantec, BitDefender | Yes CYREN |
Kolab | Yes | ? | ? | Yes | Yes | ? | ? | ? | Optional with spamassassin etc. | Yes | Optional (via content filter interface) | Optional (via content filter interface) |
Mailsite | Yes | Yes | Yes | Yes | Yes | ? | ? | No | Yes | Yes | Yes | Yes |
Mailtraq | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
MDaemon | Yes | Yes (via SpamAssassin) | Yes | Yes | Yes | Yes | Yes | Yes | Yes (via SpamAssassin) | Yes (via Content Filter) | Optional Cyren, ClamAV | Yes SpamAssassin |
Mercury Mail Transport System | Yes | ? | ? | Yes (GreyWall extension) | ? | ? | ? | ? | Yes (SpamHalter extension) | ? | Yes (ClamWall extension) | ? |
Microsoft Exchange Server | Yes (2003 & later) | ? | ? | Yes | Yes | Optional (Signing only via 3rd Party Extensions) | ? | Yes (2003 & later) | ? | ? | ? | ? |
NetMail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
OpenSMTPD | ? | ? | ? | ? | Yes | Optional [40] | Optional [41] | ? | ? | ? | ? | ? |
Oracle Communications Messaging Server | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Optional with spamassassin etc. | Yes | Optional any | Optional any |
Postfix | Yes | ? | ? | Yes | Yes | Optional [42] | Optional [43] | ? | Optional with spamassassin etc. | Yes | Optional (via content filter interface) | Optional (via content filter interface) |
qmail | ? | ? | ? | Yes | ? | ? | ? | ? | No | ? | No | No |
Scalix | Yes | Yes (via Scalix AntiSpam powered by Cyren or SpamAssassin) | Yes (via Scalix AntiSpam powered by Cyren or SpamAssassin) | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes (via Scalix ZeroHour AntiVirus powered by Cyren or ClamAV) | Yes |
Sendmail | Yes | Yes (via milter/SA) | ? | Yes | Optional | Optional [42] | Optional [43] | ? | Optional with spamassassin etc. | Yes | Yes ClamAV | Yes SpamAssassin |
SparkEngine | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
UW IMAP | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
WinGate | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Zarafa | External [14] | External [14] | External [14] | External [14] | External [14] | External [14] | External [14] | External [14] | External [14] | External [14] | External [14] | External [14] |
Zimbra | Yes | Yes (via SpamAssassin) | ? | Yes (via Cluebringer Policy Daemon) | Yes | Yes | ? | Yes | Yes | Yes (partially) | Yes (via ClamAV, optionally any via Amavisd) | Yes (via SpamAssassin) |
Mail Server | DNSBL | SURBL | Spamtraps | Greylisting | SPF | DKIM | DMARC | Tarpit | Bayesian filters | Regular expressions | Embedded Antivirus | Embedded Antispam |
The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typically use SMTP only for sending messages to a mail server for relaying, and typically submit outgoing email to the mail server on port 587 or 465 per RFC 8314. For retrieving messages, IMAP is standard, but proprietary servers also often implement proprietary protocols, e.g., Exchange ActiveSync.
The Maildir e-mail format is a common way of storing email messages on a file system, rather than in a database. Each message is assigned a file with a unique name, and each mail folder is a file system directory containing these files. Maildir was designed by Daniel J. Bernstein circa 1995, with a major goal of eliminating the need for program code to handle file locking and unlocking through use of the local filesystem.
Exim is a mail transfer agent (MTA) used on Unix-like operating systems. Exim is a free software distributed under the terms of the GNU General Public License, and it aims to be a general and flexible mailer with extensive facilities for checking incoming e-mail.
A message delivery agent (MDA), or mail delivery agent, is a computer software component that is responsible for the delivery of e-mail messages to a local recipient's mailbox. It is also called a local delivery agent (LDA).
GNU Mailman is a computer software application from the GNU Project for managing electronic mailing lists. Mailman is coded primarily in Python and currently maintained by Abhilash Raj. Mailman is free software, licensed under the GNU General Public License.
Messaging Application Programming Interface (MAPI) is an API for Microsoft Windows which allows programs to become email-aware. While MAPI is designed to be independent of the protocol, it is usually used to communicate with Microsoft Exchange Server.
Pegasus Mail is a proprietary email client for Microsoft Windows. It was originally released in 1990 on NetWare networks with MS-DOS and later Apple Macintosh clients, before being ported to Windows which is now the only platform actively supported. Since its inception it has been developed by David Harris and is donationware after having previously been freeware.
Postfix is a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail.
The Cyrus IMAP server is electronic mail server software developed by Carnegie Mellon University. It differs from other Internet Message Access Protocol (IMAP) server implementations in that it is generally intended to be run on sealed servers, where normal users cannot log in.
Dovecot is an open-source IMAP and POP3 server for Unix-like operating systems, written primarily with security in mind. Timo Sirainen originated Dovecot and first released it in July 2002. Dovecot developers primarily aim to produce a lightweight, fast and easy-to-set-up open-source email server.
The UW IMAP server was the reference server implementation of the Internet Message Access Protocol. It was developed at the University of Washington by Mark Crispin and others.
Opportunistic TLS refers to extensions in plain text communication protocols, which offer a way to upgrade a plain text connection to an encrypted connection instead of using a separate port for encrypted communication. Several protocols use a command named "STARTTLS" for this purpose. It is a form of opportunistic encryption and is primarily intended as a countermeasure to passive monitoring.
Bynari is a defunct company based in Dallas, developing server and email software, mainly known for its Insight Family, similar to Microsoft Exchange Server with Outlook.
The Courier Mail Server is a mail transfer agent (MTA) server that provides SMTP, IMAP, POP3, SMAP, webmail, and mailing list services with individual components. It is best known for its IMAP server component.
An e-mail agent is a program that is part of the e-mail infrastructure, from composition by sender, to transfer across the network, to viewing by recipient. The best-known are message user agents and message transfer agents, but finer divisions exist.
Ipswitch IMail Server is an email server application with groupware functionality that runs on Microsoft Windows OS. It was developed in 1994 by Ipswitch, Inc., a software company based in Lexington, Massachusetts.
MailEnable is a Windows-based, commercial email server distributed by MailEnable Pty. Ltd, an Australian-based software company which was established in 2002.
Kopano is an open-source groupware application suite originally based on Zarafa. The initial version of Kopano Core (KC) was forked from the then-current release of Zarafa Collaboration Platform, and superseded ZCP in terms of lineage as ZCP switched to maintenance mode with patches flowing from KC. Kopano WebApp similarly descended from Zarafa WebApp. Since October 2017, Kopano Core is also known more specifically as Kopano Groupware Core, since Kopano B.V. developed more products that were not directly requiring groupware components.
To me one of the lovely features of pipes is the way it reinforces the notion of toolbox…
This software is released under the GPL, version 3 (see COPYING.GPL).
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