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 | CLRTXT, CRAM-MD5, DIGEST-MD5, APOP, GSSAPI, NTLM, MSN, SESSIONID, External Authentication Plug-in |
| 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 |
| 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 | ? |
| MailSite Fusion | 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 |
| Meldware Mail Server | Yes | No | Yes | Yes | Yes | Yes | ? |
| 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 | ? | ? | ? | ? | ? | ? | ? |
| 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 |
Read more about this topic: Comparison Of Mail Servers