Comparison of mail servers
From Infogalactic: the planetary knowledge core
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 toolbox[1] 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
Server OS support | Features | Storage | 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 5 users / calendar 5 users) |
BlueMind | Yes | No | No | Yes | Yes | Yes | Yes | Yes | Yes | ? | No | Yes | Yes | Yes | Yes | Yes | Yes | AGPL v3 |
Citadel | Yes | No | Yes | Yes | Yes | Yes | No | 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[2] |
Cyrus IMAP | Yes | No | Yes | No | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | No | No | Yes (indexes) | Yes | Yes | 4-clause BSD[3] |
Dovecot | Yes[4] | No[4] | Yes[4] | No | Yes | Yes | Yes | No | 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 |
Haraka | Yes | Yes | Yes | Yes | No | No | No | Yes | No | Yes | No | Yes | No | No | Yes | Yes | Yes | MIT |
Hectane | Yes | Yes | Yes | Yes | No | No | No | Yes | No | Yes | No | Yes | No | No | No | Yes | No | MIT |
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 | Yes | Yes | Yes | No | Yes | Yes | No | Yes | Yes | No | GNU AGPL |
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 |
Ipswitch IMail Server | No | Yes | No | Yes | Yes | Yes | ? | Yes | Yes | ? | No | Yes | Yes | Yes | No | Yes | No | Proprietary |
Kerio Connect | Yes | Yes | 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 |
Mailenable | No | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | No | Proprietary |
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 |
MDaemon Messaging Server | No | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | No | Proprietary |
Mercury Mail Transport System | No | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | ? | No | Yes | Yes | No | No | Yes | No | Proprietary donationware |
Microsoft Exchange Server | No | Yes | No | Yes | Yes | Yes | Yes[7][8] | Yes | Yes | Yes (2007 sp1 onwards)[9] | Yes | Yes | Yes | Yes | ESE only | Yes (up to 2003 only)[10] | Yes | Proprietary |
Momentum | Yes | No | No | Yes | No | No | No | Yes | No | Yes | No | Yes | No | No | Yes | Yes | No | 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[11] |
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[12] |
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 |
Synovel Collabsuite | Yes | No | No | Yes | Yes | Yes | ? | Yes | Yes | ? | ? | Yes | Yes | No | Yes | Yes | ? | Proprietary with OSS parts, Freeware and paid editions[13] |
UW IMAP | Yes | Yes | Yes | No | Yes | Yes | Yes | No | Yes | ? | No | Yes | WebPine | No | Yes (Indexes) | Yes | No | Apache License 2.0[14] |
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 | No | ? | ? | ? | No | Yes | No | No | Yes | No | No | Proprietary (unlimited private/commercial use, support with SLA requires a license) |
Zarafa | Yes | No | No | External[15] | Yes | Yes | Yes | External[15] | Yes | No | No | Yes | Yes | Yes | Yes | Yes | No | AGPLv3, free and paid editions[16] |
Zentyal | Yes | No | No | Yes | Yes | Yes | Yes | Yes | Yes | No | No | Yes | Yes | Yes | Yes | Yes | No | GPLv2[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 |
Server OS support | Features | Storage | Users |
Authentication
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 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 |
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, GNU SASL, CRAM-MD5, Heimdal GSSAPI, 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 |
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, NTLM |
Ipswitch IMail Server | Yes | No | Yes | Yes | Yes | Yes | Active Directory, Windows authentication, CRAM-MD5, 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. |
Kerio Connect | Yes | Yes | Yes | Yes | Yes | Yes | Active Directory, Apple Open Directory, Pluggable Authentication Modules, PLAIN, LOGIN, CRAM-MD5, internal user database |
MagicMail | Yes | No | No | Yes | Yes | No | ? |
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, LOGIN,[19] NTLM |
Momentum | Yes | No | No | Yes | Yes | Yes | PLAIN, LOGIN, CRAM-MD5, LDAP |
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. |
WinGate | Yes | Yes | Yes | Yes | Yes | No | NT Domain, Active Directory, CRAM-MD5, SASL PLAIN, SASL LOGIN |
Zarafa | Yes | Yes | No | Yes | Yes | Yes | 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 | Filesystem | Database | LDAP | Other |
Antispam features
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 | Yes | No | No |
Apache James | ? | ? | ? | ? | ? | ? | ? | ? | Yes | ? | Yes ClamAV[20] | Optional (Apache SpamAssassin) |
Atmail | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | Yes ClamAV | Yes SpamAssassin and Exim ACLs |
Axigen | Yes | Yes[21] | No | Yes | Yes | ? | ? | No | Yes, in SpamAssassin | Yes | Yes Commtouch | Yes SpamAssassin |
Citadel | Yes | Yes | No | No | Optional (via SpamAssassin) | ? | ? | No | Optional (via SpamAssassin) | No | Optional (ClamAV) | Optional (SpamAssassin) |
CommuniGate Pro | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Optional | Yes | Optional Kaspersky Lab, McAfee, Sophos, Cloudmark (via plugins) | Optional SpamCatcher, Cloudmark (via plugins) |
Courier Mail Server | Yes | ? | Yes | Yes[22] | Yes | Yes[23] | ? | Yes | Yes[22] | Yes[22] | Yes Clamav | Yes[22] |
Dovecot | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Eudora Internet Mail Server | Yes | ? | Yes | Yes | ? | ? | ? | ? | ? | ? | ? | ? |
Exim | Yes | Yes | Yes | Yes | Optional at build time | Yes | Optional at build time | 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 Commtouch, Authentium | Yes Commtouch |
GroupWise | Yes | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
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 Lotus Domino | Yes[24] | ? | ? | ? | No[25] | ? | ? | ? | ? | ? | ? | ? |
IceWarp Mail Server | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Yes | Yes | Yes | Yes |
Ipswitch IMail Server | Yes | Yes | No | No | Yes | Yes[26] | Yes[27] | No | Yes | Yes | Yes Symantec, BitDefender | Yes Commtouch |
Kolab | Yes | ? | ? | Yes | Yes | ? | ? | ? | Optional with spamassassin etc. | Yes | Optional (via content filter interface) | Optional (via content filter interface) |
Kerio Connect | Yes | Yes | ? | Yes | Yes | Yes | ? | Yes | Yes | Yes | Optional Sophos + optional secondary (dual) | Yes |
MagicMail | Yes | No | Yes | No | ? | ? | ? | ? | No | Yes | Yes | Yes |
Mailsite | Yes | Yes | Yes | Yes | Yes | ? | ? | No | Yes | Yes | Yes | Yes |
Mailtraq | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
MDaemon Messaging Server | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Optional Kaspersky Lab | Yes |
Mercury Mail Transport System | Yes | ? | ? | Yes (GreyWall extension) | ? | ? | ? | ? | Yes (SpamHalter extension) | ? | Yes (ClamWall extension) | ? |
Microsoft Exchange Server | Yes (2003 & later) | ? | ? | Yes | Yes | ? | ? | Yes (2003 & later) | ? | ? | ? | ? |
Momentum | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
NetMail | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
OpenSMTPD | ? | ? | ? | ? | Yes | Yes [2] | ? | ? | ? | ? | ? | ? |
Oracle Communications Messaging Server | Yes | Yes | Yes | Yes | Yes | ? | ? | Yes | Optional with spamassassin etc. | Yes | Optional any | Optional any |
Postfix | Yes | ? | ? | Yes | Yes | Optional [28] | Optional [29] | ? | Optional with spamassassin etc. | Yes | Optional (via content filter interface) | Optional (via content filter interface) |
qmail | ? | ? | ? | Yes | ? | ? | ? | ? | No | ? | No | No |
Sendmail | Yes | Yes (via milter/SA) | ? | Yes | Optional | Optional [28] | Optional [29] | ? | Optional with spamassassin etc. | ? | Yes ClamAV | Yes SpamAssassin |
SparkEngine | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Synovel Collabsuite | Yes | Yes | Yes | Yes | Yes | ? | ? | ? | Yes | Yes | YesClamAV | Yes SpamAssassin |
UW IMAP | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
WinGate | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? | ? |
Xeams | ? | ? | Yes | Yes | Yes | ? | ? | ? | ? | ? | Optional ClamAV | Yes (Proprietary) |
Zarafa | External[15] | External[15] | External[15] | External[15] | External[15] | External[15] | External[15] | External[15] | External[15] | External[15] | External[15] | External[15] |
Zimbra | Yes | ? | ? | ? | Yes | Yes | ? | Yes | Yes | ? | Yes ClamAV | Yes SpamAssassin |
Mail Server | DNSBL | SURBL | Spamtraps | Greylisting | SPF | DKIM | DMARC | Tarpit | Bayesian filters | Regular expressions | Embedded Antivirus | Embedded Antispam |
See also
References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ See COPYING file in the distribution
- ↑ https://cyrusimap.org/mediawiki/index.php/Downloads#Licensing
- ↑ 4.0 4.1 4.2 Dovecot Operating System Compatibility. Retrieved on 2008-09-03.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ See NOTICE file in the distribution
- ↑ http://technet.microsoft.com/en-us/library/cc540463(EXCHG.80).aspx
- ↑ http://technet.microsoft.com/en-us/library/ff848256.aspx
- ↑ http://technet.microsoft.com/en-us/library/bb629624(EXCHG.80).aspx
- ↑ Exchange Installable File System (ExIFS)
- ↑ http://www.open-xchange.com/misc/licenses/
- ↑ Contains jurisdiction selection and IBM Public License-style indemnification clause.
- ↑ http://www.synovel.com/collab/editions
- ↑ UW IMAP Server Documentation
- ↑ 15.00 15.01 15.02 15.03 15.04 15.05 15.06 15.07 15.08 15.09 15.10 15.11 15.12 15.13 Zarafa Collaboration Platform architecture diagram. Retrieved on 2011-12-10.
- ↑ http://www.zarafa.com/content/scope-and-benefits
- ↑ http://www.zentyal.org/
- ↑ [1]
- ↑ http://support2.gwava.com/kb/?View=entry&EntryID=1605
- ↑ http://james.apache.org/server/3/dev-provided-mailets.html#ClamAVScan, Documentation for build-in ClamAV-Mailet, visited on 2013-03-19.
- ↑ via Kaspersky anti-spam add-on
- ↑ 22.0 22.1 22.2 22.3 with Courier-pythonfilter filtering framework
- ↑ Two DKIM filters can be found in Courier-MTA's links page
- ↑ http://www-01.ibm.com/support/docview.wss?uid=swg21102611
- ↑ 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
- ↑ http://www.imailserver.com/products/imail-secure-server/
- ↑ http://www.imailserver.com/support/patches-upgrades/imail-server-v12-5-2/
- ↑ 28.0 28.1 via opendkim milter
- ↑ 29.0 29.1 via opendmarc milter