GreenMail is an intuitive and easy-to-use test suite of email servers for testing purposes. Supports SMTP, POP3, IMAP with SSL socket support.

GreenMail is the first project that offers a test framework for both receiving and retrieving emails from Java.

GreenMail is useful in the following scenarios:

SENDING

• System testing an application. GreenMail responds like a regular SMTP server but does not deliver any email, which enables it to be used in real life applications and real test cases.  Messages can easily be extracted, verified, and modified. Support for SMTPS (SSL) is enabled.
• GreenMail is an excellent choice for unit testing code that needs to send email with a succinct, efficient (non-polling) way to wait for messages to arrive, retrieve, verify. and modify messages.
• Note that retrieval of emails can be made with a simple java method or through a provided POP3, IMAP retriever helper class.
• GreenMail SMTP is a far better and powerful than http://dumbster.sourceforge.net while still being lightweight and fast. Dumbster has a hard to use API for retrieving messages and is using polling wait for some of its operations. Dumbster is only for SMTP testing, GreenMail is an entire email test solution.

RETRIEVING

• Again GreenMail can be used for system or unit testing an application needing to use POP3 or IMAP  by responding like a standard compliant POP3 or IMAP server. Support for SMTPS (SSL) is enabled.
• GreenMail ships with an easy-to-use helper class for retrieving.

SENDING AND RETRIEVING

• GreenMail can easily been configured to use all or a combination of ports, protocols, and bind addresses.  For example it’s possible to run GreenMail on SMTP, POP3, POP3S and IMAPS ports as easily as only SMTP.
• Many systems might already be running these servers or don’t allow non root users to open the default ports which is why GreenMail ships with a special configuration for testing.