Comparison of mail servers

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This is a comparison of mail servers: mail transfer agents, mail delivery agents, and other computer software which provide e-mail services.

Linux-based mail servers are built using a number of components because a Linux environment is, by default, a multi-user operating system. A stock Linux server already has internal mail. To allow the server to send external emails, a Mail Transfer Agent such as sendmail, postfix or exim is required. Mail is read either through direct access (shell login) or mailbox protocols like POP and IMAP.

Feature comparison[edit]

RServer OS supportFeaturesStorageUsers
Mail serverLinux/UnixWindowsMac OSSMTPPOP3IMAPIMAP IDLESMTP over TLSPOP over TLSIPv6NNTPSSLWebmailActiveSyncDatabaseFilesystemOtherLicense
agorum coreYesYesNoYesNoYes?NoNo?NoYesYesNoYesNoNoGPLv2
Apache JamesYesYesYesYesYesYesYesYesYes?YesYesNoNoYesYesNoASLv2
AtmailYesNoYesYesYesYesYesYesYes?NoYesYesYesYesYesNoProprietary (100 user/30 day demo)
AxigenYesYesNoYesYesYesYesYesYesNoNoYesAjax & BasicYesNoNoYesProprietary (free version: email 100 users / calendar 5 users)
CitadelYesNoYesYesYesYesNoYesYesYes?YesYesNoYesNoNoGPLv3
CommuniGate ProYesYesYesYesYesYesYesYesYesYesNoYesYesYesYesYesYesProprietary (Free for up to 5 users)
Courier Mail ServerYesNoYesYesYesYesYesYesYesYes?YesYesNoNomaildirNoGPLv3[1]
Cyrus IMAPYesNoYesNoYesYesYesNoYesYesYesYesNoNoYes (indexes)YesYes4-clause BSD[2]
DovecotYes[3]No[3]Yes[3]NoYesYesYesNoYesYesNoYesNoNoYesmaildir, mbox, dboxNoMixed: MIT and LGPL 2.1[4]
Eudora Internet Mail ServerNoNoYesYesYesYes?NoNo?NoNoNoNoNoNoYesProprietary
EximYesYes (via Cygwin)YesYesDovecot, UW IMAPDovecot, UW IMAPDovecot, UW IMAPYesNoYesNoYesNoNoYesYesNoGPLv2+[5]
FirstClassYesYesYesYesYesYes?YesYes?YesYesYesYesYesYesYesProprietary
Gordano Messaging SuiteYesYesNoYesYesYes?YesYes?NoYesYesNoYesYesYesProprietary
GroupWiseYesYesNoYesYesYes?YesYes??YesYesYesYesNoNoProprietary
HarakaYesYesYesYesNoNoNoYesNoYesNoYesNoNoYesYesYesMIT
Mail serverLinux/UnixWindowsMac OSSMTPPOP3IMAPIMAP IDLESMTP over TLSPOP over TLSIPv6NNTPSSLWebmailActiveSyncDatabaseFilesystemOtherLicense
hMailServerNoYesNoYesYesYesYesYesYesYesNoYesYesNoYesYesNoGNU AGPL
IBM Lotus DominoYesYesNoYesYesYes?YesYes?YesYesYesYesYesNoNoProprietary
IceWarp Mail ServerYesYesNoYesYesYesYesYesYesYesNoYesYesYesYesYesNoProprietary
Ipswitch IMail ServerNoYesNoYesYesYes?YesYes?NoYesYesYesNoYesNoProprietary
Kerio ConnectYesYesYesYesYesYesYesYesYesNoYesYesYesYesYesYesNoProprietary
KolabYesNoNoYesYesYesYesYesYesYesYesYesYesYesYesYesYesGPLv3
MagicMailYesNoNoYesYesYes?YesYes?NoYesYesNoYesYesYesProprietary
MailsiteNoYesNoYesYesYes?YesYes?NoYesYesYesYesYesYesProprietary
MailtraqNoYesNoYesYesYesYesYesYes?YesYesYesNoYesYesYesProprietary
MDaemon Mail ServerNoYesNoYesYesYesYesYesYesNoNoYesYesYesYesYesNoProprietary
Mercury Mail Transport SystemNoYesNoYesYesYes?YesYes?NoYesYesNoNoYesNoProprietary donationware
Microsoft Exchange ServerNoYesNoYesYesYesYes[6][7]YesYesYes (2007 sp1 onwards)[8]YesYesYesYesESE onlyYes (up to 2003 only)[9]YesProprietary
NetMailYesYesNoYesYesYes?YesYes??YesYesNoYesNoNoProprietary
OpenSMTPDYesNoYesYesNoNoNoYesNoYesNoYesNoNopossible through custom backendsYesNoISC
Open-XchangeYesNoNoYesYesYes?YesYes??YesYesYesYesNoNoProprietary/SaaS, with open-source parts[10]
Mail serverLinux/UnixWindowsMac OSSMTPPOP3IMAPIMAP IDLESMTP over TLSPOP over TLSIPv6NNTPSSLWebmailActiveSyncDatabaseFilesystemOtherLicense
Oracle Communications Messaging ServerYesNoNoYesYesYes?YesYes?NoYesYesNoYesYesNoProprietary
PostfixYesNoYesYesDovecot, UW IMAPDovecot, UW IMAPDovecot, UW IMAPYesNoYesNoYesNoNoYesYesYesIBM Public License
qmailYesNoYesYesYesDovecot, UW IMAPDovecot, UW IMAPNoDovecot, UW IMAPvia Qsmtp?NoNoNo(cdb)YesNoPublic domain
QpopperYesvia CygwinYesNoYesNoNoNoYes?NoYesNoNoNoYesYesBSD-style, GPL-incompatible[11]
SendmailYesNoYesYesDovecot, UW IMAPDovecot, UW IMAPDovecot, UW IMAPYesNoYesNoYesNoNo?Yes?Sendmail License
SparkEngineYesYesYesYesNoNoNoYesNo?NoYesNoNoYesYesYesProprietary
Synovel CollabsuiteYesNoNoYesYesYes?YesYes??YesYesNoYesYes?Proprietary with OSS parts, Freeware and paid editions[12]
UW IMAPYesYesYesNoYesYesYesNoYes?NoYesWebPineNoYes (Indexes)YesNoApache License 2.0[13]
WinGateNoYesNoYesYesYesYesYesYesNoNoYesYesNoNoYesNoProprietary
ZarafaYesNoNoExternal[14]YesYesYesExternal[14]YesNoNoYesYesYesYesYesNoAGPLv3, free and paid editions[15]
ZimbraYesNoYesYesYesYesYesYesYesNoNoYesYesYesYesYesNoZPL and proprietary editions[16]
MailenableNoYesNoYesYesYesYesYesYesYesNoYesYesYesYesYesNoProprietary
Mail serverLinux/UnixWindowsMac OS XSMTPPOP3IMAPIMAP IDLESMTP over TLSPOP over TLSIPv6NNTPSSLWebmailActiveSyncDatabaseFilesystemOtherLicense
RadifServer OS supportFeaturesStorageUsers

Authentication[edit]

Mail serverSMTP AUTHPOP before SMTPAPOPFilesystemDatabaseLDAPOther
agorum coreYesNoNoNoYesYesPLAIN, LOGIN, CRAM-MD5, NTLM
Apache JamesYes???YesYesPLAIN, LOGIN
AtmailYesYesYesYesYesYesPLAIN, LOGIN, CRAM-MD5, DIGEST-MD5, Active Directory, any LDAP-compatible source
AxigenYesNoYesNoNoYesGSSAPI, CRAM-MD5, DIGEST-MD5, APOP, CLRTXT, LOGIN, PLAIN, LDAP, Internal
CommuniGate ProYesYesYesYesYesYesActive Directory (LDAP), CLRTXT, CRAM-MD5, DIGEST-MD5, APOP, GSSAPI, NTLM, MSN, SESSIONID, External Authentication Plug-in. Also supports X.509 PKI auth via STARTTLS/SSL
Courier Mail ServerYesYesYesYesYesYesManaged by Courier authentication library which can use PAM, Userdb, PostgreSQL(beta), MySQL, LDAP, and EXTERNAL.
Cyrus IMAPNoYesYesYesYesYesSupports 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, DIGEST-MD5, EXTERNAL, GSSAPI, LOGIN, NTLM, OTP, PASSDSS, PLAIN, SRP
DovecotNoYesYesYesYesYesNot an SMTP server, but offers SASL to MTAs. http://wiki.dovecot.org/DovecotFeatures http://wiki.dovecot.org/Authentication. 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, DIGEST-MD5, SCRAM-SHA1, EXTERNAL, GSSAPI, NTLM, OTP, SKEY, RPA.
Eudora Internet Mail ServerYesNoYesYesNoNoCRAM-MD5, DIGEST-MD5, PLAIN, LOGIN
EximYesYesYesYesYesYesCyrus SASL, Dovecot SASL, GNU SASL, CRAM-MD5, Heimdal GSSAPI, PLAIN, LOGIN, SPA
FirstClassYes??YesYesYes
Gordano Messaging SuiteYesYesYesNoYesYesPLAIN, LOGIN, CRAM-MD5, DIGEST-MD5, APOP, ODBC, Active Directory, NT Domain
GroupWiseYesYesYesYesYesYeseDirectory, Any LDAPv3-compliant source
HarakaYesNoNoYesYesYesProxy to other server, any other mechanism via AUTH plugins.
IceWarp Mail ServerYesYesYesYesYesYesPLAIN, LOGIN, CRAM-MD5, NTLM
Ipswitch IMail ServerYesNoYesYesYesYesActive Directory, Windows authentication, CRAM-MD5, PLAIN, LOGIN
KolabYesYesYesYesYesYesKolab employs Cyrus and Postfix and thus supports all Cyrus SASL authentication methods and X.509 PKI auth via STARTTLS and EXTERNAL.
Kerio ConnectYesYesYesYesNoYesActive Directory, Apple Open Directory, ActiveSync, Pluggable Authentication Modules
MagicMailYesNoNoYesYesNo?
MailsiteYesNoYesYesYesYesNT Domain, Active Directory, PLAIN, LOGIN, NTLM, SCRAM-MD5, CRAM-MD5
MailtraqYesYesYesYesYesYesNT Domain, Active Directory, Local Directory
MDaemon Mail ServerYesYesYesNoYesYesActive Directory, PLAIN, CRAM-MD5, LOGIN
Mercury Mail Transport SystemYesYesYesYesNo?Internal, LOGIN, PLAIN, CRAM-MD5, Netware, LDAP?, partial NT Domain
Microsoft Exchange ServerYes?YesNoNoYesActive Directory, LOGIN,[17] NTLM
NetMailYesYesYesYesYesYeseDirectory, LDAP
Oracle Communications Messaging ServerYesYesYesYesYesYesPlain, Login, CRAM-MD5, Digest-MD5, Certificate
OpenSMTPDYesNoNoYesYesYesBy default PLAIN and LOGIN over SSL only, Certificates, bsd_auth and PAM. Supports adding new authentication mechanisms through custom backends.
PostfixYesNoNoYesYesYesSupports all Cyrus SASL authentication methods except for APOP.
QpopperNoYesYesYesYesYesPluggable Authentication Modules,GSSAPI, CRAM-MD5, DIGEST-MD5, APOP, PLAIN, LDAP, CMU SASL library, Kerberos
qmailwith patchwith vpopmailYesYesYesYesWorks with any checkpassword utility. The original supports only LOGIN and PLAIN. Alternate checkpassword utilities support authentication against PAM, LDAP, and databases.
SendmailYesYesNoYesYesYesSupports all Cyrus SASL authentication methods except for APOP. Also supports X.509 PKI auth via STARTTLS and EXTERNAL.
WinGateYesYesYesYesYesNoNT Domain, Active Directory, CRAM-MD5, SASL PLAIN, SASL LOGIN
ZarafaYesYesNoYesYesYesInternal, Active Directory, any LDAP-compatible source, Unix
ZimbraYesNoYesYesYesYesInternal, LDAP, Open LDAP, Active Directory
Mail serverSMTP AUTHPOP before SMTPAPOPFilesystemDatabaseLDAPOther

Antispam Features[edit]

Mail ServerDNSBLSURBLSpamtrapsGreylistingSPFDKIMDMARCTarpitBayesian filtersRegular expressionsEmbedded AntivirusEmbedded Antispam
agorum coreNoNoNoNoNo??NoNoYesNoNo
Apache James????????Yes?Yes ClamAV[18]Optional (Apache SpamAssassin)
AtmailYesYesYesYesYes??YesYesYesYes ClamAVYes SpamAssassin and Exim ACLs
AxigenYesYes[19]NoYesYes??NoYes, in SpamAssassinYesYes CommtouchYes SpamAssassin
CitadelYesYesNoNoOptional (via SpamAssassin)??NoOptional (via SpamAssassin)NoOptional (ClamAV)Optional (SpamAssassin)
CommuniGate ProYesYesYesNoYes??YesOptionalYesOptional (ClamAV)Optional (via SpamAssassin)
Courier Mail ServerYes?YesYes[20]Yes??YesYes[20]Yes[20]Yes ClamavYes[20]
Dovecot????????????
Eudora Internet Mail ServerYes?YesYes????????
EximYesYesYesYesOptional at build timeYesOptional at build timeYesOptional with spamassassin etc.YesOptional anyOptional any
FirstClassYesYesNo?Yes??YesYesYesYes Symantec?
Gordano Messaging SuiteYesYesYesYesYes??YesYesYesYes Commtouch, AuthentiumYes Commtouch
GroupWiseYes???????????
HarakaYesYesYesYesYesYes?YesOptional with spamassassin etc.YesOptional ClamAV, AVG, any via pluginsOptional SpamAssassin, MessageSniffer
hMailServerYesYesNoYesYesYes?NoNoYesYes ClamAVYes SpamAssassin
IBM Lotus DominoYes[21]???No[22]???????
IceWarp Mail ServerYesYesYesYesYes??YesYesYesYesYes
Ipswitch IMail ServerYesYesNoNoYes??NoYesYesYes Symantec, BitDefenderYes Commtouch
KolabYes??YesYes???Optional with spamassassin etc.YesOptional (via content filter interface)Optional (via content filter interface)
Kerio ConnectYesYes?NoYesYes?YesYes?Optional Sophos + optional secondary (dual)Yes
MagicMailYesNoYesNo????NoYesYesYes
MailsiteYesYesYesYesYes??NoYesYesYesYes
Mailtraq????????????
MDaemon Mail ServerYesYesYesYesYes??YesYesYesOptional Kaspersky LabYes
Mercury Mail Transport SystemYes??Yes (GreyWall extension)????Yes (SpamHalter extension)?Yes (ClamWall extension)?
Microsoft Exchange ServerYes (2003 & later)??YesYes??Yes (2003 & later)????
NetMail????????????
OpenSMTPD????YesYes [2]??????
Oracle Communications Messaging ServerYesYesYesYesYes??YesOptional with spamassassin etc.YesOptional anyOptional any
PostfixYes??YesYesOptional [23]Optional [24]?Optional with spamassassin etc.YesOptional (via content filter interface)Optional (via content filter interface)
qmail???Yes????No?NoNo
SendmailYesYes (via milter/SA)?YesOptionalOptional [23]Optional [24]?Optional with spamassassin etc.?Yes ClamAVYes SpamAssassin
SparkEngine????????????
Synovel CollabsuiteYesYesYesYesYes???YesYesYesClamAVYes SpamAssassin
UW IMAP????????????
WinGate????????????
ZarafaExternal[14]External[14]External[14]External[14]External[14]External[14]External[14]External[14]External[14]External[14]External[14]External[14]
ZimbraYes???YesYes?YesYes?Yes ClamAVYes SpamAssassin
Mail ServerDNSBLSURBLSpamtrapsGreylistingSPFDKIMDMARCTarpitBayesian filtersRegular expressionsEmbedded AntivirusEmbedded Antispam

See also[edit]

Notes and references[edit]

  1. ^ See COPYING file in the distribution
  2. ^ https://cyrusimap.org/mediawiki/index.php/Downloads#Licensing
  3. ^ a b c Dovecot Operating System Compatibility. Retrieved on 2008-09-03.
  4. ^ "Dovecot licensing information: COPYING". Retrieved 2008-09-03. 
  5. ^ See NOTICE file in the distribution
  6. ^ http://technet.microsoft.com/en-us/library/cc540463(EXCHG.80).aspx
  7. ^ http://technet.microsoft.com/en-us/library/ff848256.aspx
  8. ^ http://technet.microsoft.com/en-us/library/bb629624(EXCHG.80).aspx
  9. ^ Exchange Installable File System (ExIFS)
  10. ^ http://www.open-xchange.com/misc/licenses/
  11. ^ Contains jurisdiction selection and IBM Public License-style indemnification clause.
  12. ^ http://www.synovel.com/collab/editions
  13. ^ UW IMAP Server Documentation
  14. ^ a b c d e f g h i j k l m n Zarafa Collaboration Platform architecture diagram. Retrieved on 2011-12-10.
  15. ^ http://www.zarafa.com/content/scope-and-benefits
  16. ^ [1]
  17. ^ http://support2.gwava.com/kb/?View=entry&EntryID=1605
  18. ^ http://james.apache.org/server/3/dev-provided-mailets.html#ClamAVScan, Documentation for build-in ClamAV-Mailet, visited on 2013-03-19.
  19. ^ via Kaspersky anti-spam add-on
  20. ^ a b c d with Courier-pythonfilter filtering framework
  21. ^ http://www-01.ibm.com/support/docview.wss?uid=swg21102611
  22. ^ http://www-01.ibm.com/support/docview.wss?rs=463&context=SSKTMJ&dc=DB520&uid=swg21227751&loc=en_US&cs=UTF-8&lang=en&rss=ct463lotus
  23. ^ a b via opendkim milter
  24. ^ a b via opendmarc milter