Linux-based mail servers are built using a number of components due to the fact that 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.
| 00000 !Radif |
00000 !Server OS support |
00000 !Features |
00000 !Storage |
00000 !Users |
| Mail server |
Linux/Unix |
Windows |
Mac OS |
SMTP |
POP3 |
IMAP |
IMAP IDLE |
SMTP over TLS |
POP over TLS |
IPv6 |
NNTP |
SSL |
Webmail |
ActiveSync |
Database |
Filesystem |
Other |
License |
| agorum core |
Yes |
Yes |
No |
Yes |
No |
Yes |
? |
No |
No |
? |
No |
Yes |
Yes |
No |
Yes |
No |
No |
GPLv2 |
| Apache James |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
No |
No |
Yes |
Yes |
No |
ASLv2 |
| Atmail |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
? |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
Proprietary (100 user/30 day demo) |
| Axigen |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
No |
Yes |
Ajax & Basic |
Yes |
No |
No |
Yes |
Proprietary (free version: email 100 users / calendar 5 users) |
| Citadel |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
No |
Yes |
No |
No |
GPLv3 |
| CommuniGate Pro |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
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 |
Yes |
No |
No |
maildir |
No |
GPLv3[1] |
| Cyrus IMAP |
Yes |
No |
Yes |
No |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
No |
No |
Yes (indexes) |
Yes |
Yes |
4-clause BSD[2] |
| DBMail |
Yes |
via Cygwin |
Yes |
Postfix, Exim, Sendmail, qmail |
Yes |
Yes |
Yes |
Postfix, Exim, Sendmail, qmail |
Yes |
Yes |
? |
Yes |
No |
No |
PostgreSQL, MySQL, SQLite |
No |
No |
GPLv2[3] |
| Digital Integration iMail5 |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
? |
No |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Proprietary |
| Dovecot |
Yes[4] |
No[4] |
Yes[4] |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
Yes |
No |
No |
Yes |
maildir, mbox, dbox |
No |
Mixed: MIT and LGPL 2.1[5] |
| Eudora Internet Mail Server |
No |
No |
Yes |
Yes |
Yes |
Yes |
? |
No |
No |
? |
No |
No |
No |
No |
No |
No |
Yes |
Proprietary |
| Exim |
Yes |
Yes (via Cygwin) |
Yes |
Yes |
Dovecot, UW IMAP |
Dovecot, UW IMAP |
Dovecot, UW IMAP |
Yes |
No |
Yes |
No |
Yes |
No |
No |
Yes |
Yes |
No |
GPLv2+[6] |
| FirstClass |
Yes |
Yes |
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 |
? |
No |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Proprietary |
| GroupWise |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
? |
Yes |
Yes |
Yes |
Yes |
No |
No |
Proprietary |
| Hexamail Server |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
Yes |
No |
No |
Yes |
No |
Proprietary |
| Mail server |
Linux/Unix |
Windows |
Mac OS |
SMTP |
POP3 |
IMAP |
IMAP IDLE |
SMTP over TLS |
POP over TLS |
IPv6 |
NNTP |
SSL |
Webmail |
ActiveSync |
Database |
Filesystem |
Other |
License |
| hMailServer |
No |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
V 5.0 |
V 5.0 |
Yes |
No |
V 5.0 |
Yes |
No |
Yes |
No |
No |
GNU GPL (V5.0 Proprietary) |
| IBM Lotus Domino |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
No |
Proprietary |
| IceWarp Mail Server |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
Proprietary |
| IndiMail |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
Yes |
No |
Yes |
No |
No |
Yes |
Yes |
No |
GPLv3 |
| Ipswitch IMail Server |
No |
Yes |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
Yes |
Yes |
No |
Yes |
No |
Proprietary |
| JMail |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Proprietary |
| Kerio Connect |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
Proprietary |
| Kolab |
Yes |
No |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
GPLv3 |
| MagicMail |
Yes |
No |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Proprietary |
| Mailismus |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
? |
No |
Yes |
No |
No |
Yes |
Yes |
No |
Proprietary (28-day free demo) |
| Mailsite |
No |
Yes |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Proprietary |
| Mailtraq |
No |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Proprietary |
| masqmail |
Yes |
No |
Yes |
Yes |
No |
No |
No |
Yes |
No |
Yes |
No |
Yes |
No |
No |
No |
Yes |
Yes |
GPL |
| MDaemon Mail Server |
No |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
No |
Yes |
Yes |
Yes [Requires one time fee] [7] |
Yes [Requires one time fee] |
Yes |
No |
Proprietary |
| Mercury Mail Transport System |
No |
Yes |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
Yes |
No |
No |
Yes |
No |
Proprietary donationware |
| Microsoft Exchange Server |
No |
Yes |
No |
Yes |
Yes |
Yes |
Yes[8][9] |
Yes |
Yes |
Yes (2007 sp1 onwards)[10] |
Yes |
Yes |
Yes |
Yes |
ESE only |
Yes (up to 2003 only)[11] |
Yes |
Proprietary |
| Mirapoint |
Yes |
No |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Proprietary |
| NetMail |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
? |
Yes |
Yes |
No |
Yes |
No |
No |
Proprietary |
| OpenSMTPD |
Yes |
No |
Yes |
Yes |
No |
No |
No |
Yes |
No |
Yes |
No |
Yes |
No |
No |
possible through custom backends |
Yes |
No |
ISC |
| Open-Xchange |
Yes |
No |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
? |
Yes |
Yes |
Yes |
Yes |
No |
No |
Proprietary/SaaS, with open-source parts[12] |
| Mail server |
Linux/Unix |
Windows |
Mac OS |
SMTP |
POP3 |
IMAP |
IMAP IDLE |
SMTP over TLS |
POP over TLS |
IPv6 |
NNTP |
SSL |
Webmail |
ActiveSync |
Database |
Filesystem |
Other |
License |
| Oracle Communications Messaging Server |
Yes |
No |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
Yes |
No |
Yes |
Yes |
No |
Proprietary |
| Postfix |
Yes |
No |
Yes |
Yes |
Dovecot, UW IMAP |
Dovecot, UW IMAP |
Dovecot, UW IMAP |
Yes |
No |
Yes |
No |
Yes |
No |
No |
Yes |
Yes |
Yes |
IBM Public License |
| qmail |
Yes |
No |
Yes |
Yes |
Yes |
Dovecot, UW IMAP |
Dovecot, UW IMAP |
No |
Dovecot, UW IMAP |
via Qsmtp |
? |
No |
No |
No |
(cdb) |
Yes |
No |
Public domain |
| Qpopper |
Yes |
via Cygwin |
Yes |
No |
Yes |
No |
No |
No |
Yes |
? |
No |
Yes |
No |
No |
No |
Yes |
Yes |
BSD-style, GPL-incompatible[13] |
| Sendmail |
Yes |
No |
Yes |
Yes |
Dovecot, UW IMAP |
Dovecot, UW IMAP |
Dovecot, UW IMAP |
Yes |
No |
Yes |
No |
Yes |
No |
No |
? |
Yes |
? |
Sendmail License |
| SparkEngine |
Yes |
Yes |
Yes |
Yes |
No |
No |
No |
Yes |
No |
? |
No |
Yes |
No |
No |
Yes |
Yes |
Yes |
Proprietary |
| SurgeMail |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
Proprietary (free for up to 5 users) |
| Synovel Collabsuite |
Yes |
No |
No |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
? |
Yes |
Yes |
No |
Yes |
Yes |
? |
Proprietary with OSS parts, Freeware and paid editions[14] |
| UW IMAP |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
No |
Yes |
? |
No |
Yes |
WebPine |
No |
Yes (Indexes) |
Yes |
No |
Apache License 2.0[15] |
| WinGate |
No |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
No |
Yes |
Yes |
No |
No |
Yes |
No |
Proprietary |
| Xeams |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
? |
Yes |
Yes |
? |
No |
Yes |
No |
No |
No |
Yes |
No |
Freeware with support option |
| Zarafa |
Yes |
No |
No |
External[16] |
Yes |
Yes |
Yes |
External[16] |
Yes |
No |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
AGPLv3, free and paid editions[17] |
| Zimbra |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
ZPL and proprietary editions[18] |
| Mail server |
Linux/Unix |
Windows |
Mac OS X |
SMTP |
POP3 |
IMAP |
IMAP IDLE |
SMTP over TLS |
POP over TLS |
IPv6 |
NNTP |
SSL |
Webmail |
ActiveSync |
Database |
Filesystem |
Other |
License |
| zzzzz !Radif |
zzzzz !Server OS support |
zzzzz !Features |
zzzzz !Storage |
zzzzz !Users |
| Mail server |
SMTP AUTH |
POP before SMTP |
APOP |
Filesystem |
Database |
LDAP |
Other |
| agorum core |
Yes |
No |
No |
No |
Yes |
Yes |
PLAIN, LOGIN, CRAM-MD5, NTLM |
| Apache James |
Yes |
? |
? |
? |
Yes |
Yes |
PLAIN, LOGIN |
| Atmail |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
PLAIN, LOGIN, CRAM-MD5, DIGEST-MD5, Active Directory, any LDAP-compatible source |
| Axigen |
Yes |
No |
Yes |
No |
No |
Yes |
GSSAPI, CRAM-MD5, DIGEST-MD5, APOP, CLRTXT, LOGIN, PLAIN, LDAP, Internal |
| CommuniGate Pro |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Active 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 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 |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Supports all Cyrus SASL authentication methods. Also supports X.509 PKI auth via STARTTLS and EXTERNAL. |
| Cyrus SASL Library |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
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 |
| Digital Integration iMail5 |
Yes |
No |
Yes |
No |
No |
No |
|
| Dovecot |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Not 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 Server |
Yes |
No |
Yes |
Yes |
No |
No |
CRAM-MD5, DIGEST-MD5, PLAIN, LOGIN |
| Exim |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Cyrus SASL, Dovecot SASL, CRAM-MD5, PLAIN, LOGIN, SPA |
| FirstClass |
Yes |
? |
? |
Yes |
Yes |
Yes |
|
| Gordano Messaging Suite |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
PLAIN, LOGIN, CRAM-MD5, DIGEST-MD5, APOP, ODBC, Active Directory, NT Domain |
| GroupWise |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
eDirectory, Any LDAPv3-compliant source |
| Hexamail Server |
Yes |
Yes |
Yes |
Yes |
No |
Yes |
CLRTXT, CRAM-MD5, DIGEST-MD5, APOP, GSSAPI, NTLM, MSN, SESSIONID |
| IceWarp Mail Server |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
PLAIN, LOGIN, CRAM-MD5, NTLM |
| IndiMail |
Yes |
Yes |
No |
Yes |
Yes |
Yes |
CLRTXT, PLAIN, LOGIN, CRAM-MD5, CRAM-SHA1, CRAM-RIPEMD, DIGEST-MD5, APOP, Checkpassword, authindi, authldap, Pluggable Authentication Modules, Name Service Switch |
| Ipswitch IMail Server |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Active Directory, Windows authentication, CRAM-MD5, PLAIN, LOGIN |
| JMail |
Yes |
No |
Yes |
No |
No |
No |
CRAM-MD5, PLAIN, LOGIN, APOP, HTTP DIGEST. Authentication through a JID system |
| 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. |
| Kerio Connect |
Yes |
Yes |
Yes |
Yes |
No |
Yes |
Active Directory, Apple Open Directory, ActiveSync, Pluggable Authentication Modules |
| MagicMail |
Yes |
No |
No |
Yes |
Yes |
No |
? |
| Mailismus |
Yes |
No |
Yes |
Yes |
No |
No |
LOGIN, PLAIN, CRAM-MD5, EXTERNAL |
| Mailsite |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
NT Domain, Active Directory, PLAIN, LOGIN, NTLM, SCRAM-MD5, CRAM-MD5 |
| Mailtraq |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
NT Domain, Active Directory, Local Directory |
| MDaemon Mail Server |
Yes |
Yes |
Yes |
No |
Yes |
Yes |
Active Directory, PLAIN, CRAM-MD5, LOGIN |
| Mercury Mail Transport System |
Yes |
Yes |
Yes |
Yes |
No |
? |
Internal, LOGIN, PLAIN, CRAM-MD5, Netware, LDAP?, partial NT Domain |
| Microsoft Exchange Server |
Yes |
? |
Yes |
No |
No |
Yes |
Active Directory, PLAIN, NTLM |
| Mirapoint |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Plaintext, LDAP, NTLM, APOP, Kerberos_v4, Kerberos_v5, Radius, Sessionid |
| NetMail |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
eDirectory, LDAP |
| Oracle Communications Messaging Server |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Plain, Login, CRAM-MD5, Digest-MD5, Certificate |
| OpenSMTPD |
Yes |
No |
No |
Yes |
Yes |
Yes |
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 |
Supports all Cyrus SASL authentication methods except for APOP. |
| Qpopper |
No |
Yes |
Yes |
Yes |
Yes |
Yes |
Pluggable Authentication Modules,GSSAPI, CRAM-MD5, DIGEST-MD5, 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. |
| 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. |
| SurgeMail |
Yes |
Yes |
Yes |
Yes |
Yes |
Yes |
Internal, LDAP, PAM, MYSQL, ODBC, Unix Password, Windows Domain or external protocol |
| WinGate |
Yes |
Yes |
Yes |
Yes |
Yes |
No |
NT Domain, Active Directory, CRAM-MD5, SASL PLAIN, SASL LOGIN |
| Zarafa |
Yes |
Yes |
? |
Yes |
Yes |
Yes |
Internal, Active Directory, any LDAP-compatible source, Unix |
| Zimbra |
Yes |
No |
Yes |
Yes |
Yes |
Yes |
Internal, LDAP, Open LDAP, Active Directory |
| Mail server |
SMTP AUTH |
POP before SMTP |
APOP |
Filesystem |
Database |
LDAP |
Other |