Java(tm) Mailserver
- SMTP/POP3 server running under Java 2 Runtime Environment. Includes a list of features, original code base, and how-to configure it.
- http://www.jps.at/java/tools/mailserver.html

DixieMail
- A SMTP and POP3 email server. [Freeware, open source]
- http://www.ghofulpo.com/dixiemail/dixiemail.htm

Jsmtpd
- A modular SMTP daemon (mail server) written in Java. [Open source, GPL]
- http://www.jsmtpd.org

XMS
- Java 1.5 certified email application server. [Commercial]
- http://www.activsoftware.com/xms/

Dwarf Mail Server
- A full-featured SMTP/POP3/IMAP4 server with pluggable mail filters and agents for application processing. [Shareware]
- http://www.gnome.sk/Dwarf/dwarf_mail.html

Newsletter Dispenser Server
- Newsletter software capable of publishing e-mail newsletter and maintaining the subscribers. This newsletter software written in Java, provides stats and analysis for the published newsletters. [Commercial]
- http://www.newsletterdispenser.com/

POP3 Proxy
- Server which allows access to POP3 mailboxes for users who don't have direct access to them. It can be used for accessing POP3 mailboxes from multiple computers even if only one of them has a dial-up connection to Internet. [Freeware]
- http://home.tiscali.cz:8080/~cz210552/pop3proxy.html

SMTP Proxy
- SMTP mail relay. [Freeware]
- http://home.tiscali.cz:8080/~cz210552/smtpproxy.html

Java Apache Mail Enterprise Server (JAMES)
- Fully-featured mail server which handles both transport and storage, and allows for easy extensibility using MailServlets (for example: send mails as fax or voice, filter mailets, translator, mailing list, newspaper via mail). [Open Source, BSD-like]
- http://james.apache.org/

JEmail
- Very simple smtp pop3 java email server implementation with source. [Open Source,GPL]
- http://sourceforge.net/projects/jemail

JAMS
- Java mail server. Uses a JDBC database (free database InstantDB is provided) to store messages. [Open Source, GPL]
- http://www.kimble.easynet.co.uk/jams/