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About GreenMail

Introduction

GreenMail is an open source, intuitive and easy-to-use test suite of email servers for testing purposes.

Typical use cases include mail integration testing or a lightweight sand boxed mail server for development.

  • Supports SMTP, POP3 and IMAP including SSL
  • Prevents accidental email leaking to real mail servers
  • Provides different deployment models, such as a simple standalone JVM process, as a WAR module or as a docker image
  • Easily embeddable in JUnit tests for integration testing
  • Lightweight with few dependencies

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

Scenarios

GreenMail is useful in the following scenarios:

Test Your Sending Code

  • 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. Alternatively you can use a local client like Thunderbird.
  • The example below is using the GreenMail JUnit rule. See examples for hints on how to use GreenMail without the rule.

@Rule
public final GreenMailRule greenMail = new GreenMailRule(ServerSetupTest.SMTP);

@Test
public void testSend() throws MessagingException {
    GreenMailUtil.sendTextEmailTest("to@localhost", "from@localhost",
        "some subject", "some body"); // --- Place your sending code here instead
    assertEquals("some body", GreenMailUtil.getBody(greenMail.getReceivedMessages()[0]));
}
        

Test Your Retrieving Code

  • 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 POP3S and IMAPS (SSL) is also enabled.
  • Messages can be placed directly in users mailboxes or by using SMTP.
  • GreenMail ships with helper classes for sending and retrieving. See the javadocs for the Retriever.java class

@Rule
public final GreenMailRule greenMail = new GreenMailRule(ServerSetupTest.SMTP_IMAP);

@Test
public void testReceive() throws MessagingException {
    GreenMailUser user = greenMail.setUser("to@localhost", "login-id", "password");
    user.deliver(createMimeMessage()); // You can either create a more complex message...
    GreenMailUtil.sendTextEmailTest("to@localhost", "from@localhost",
        "subject", "body"); // ...or use the default messages

    assertEquals(2, greenMail.getReceivedMessages().length); // // --- Place your POP3 or IMAP retrieve code here
}
        

Sending and Retrieving

GreenMail can easily be 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.

Mocking a mail server for your development environment

GreenMail provides a JBoss GreenMail service for mocking a mail server for development. It safes you the overhead of either installing a full productive server (like Apache James).

Check out the possible deployments as webapp, standalone or standalone docker image.

Implementation

The implementation is in 100% Java with only a few library dependencies for GreenMail Core:

GreenMail contains several modules:

Source Code

You find the source on GitHub including build instructions. GreenMail is open source released under The Apache 2.0 License.

GreenMail's protocol source code is based on a cocktail of Foedus and James.

The following lists provide helpful links related to GreenMail and email integration testing.

Projects extending/wrapping GreenMail:
Articles&Blogs:
Projects using GreenMail include:
Related projects to JavaMail and testing/development:

Thanks

Special thanks to all contributors for feedback and patches!

Many thanks to JProfiler logo and JetBrains for supporting this project with free OSS licenses!

Examples

The source code of the examples can be found in the test package of GreenMail (greenmail-core/src/test/java/com/icegreen/greenmail/examples/).

Using JUnit4 rule based setup

The rule GreenMailRule provided by com.icegreen:greenmail-junit4 will take care of starting and stopping GreenMail for each test, providing a clean environment.

/** [See code on GitHub](https://github.com/greenmail-mail-test/greenmail/tree/master/greenmail-core/src/test/java/com/icegreen/greenmail/examples/ExampleRuleTest.java) */
@Rule
public final GreenMailRule greenMail = new GreenMailRule(ServerSetupTest.ALL);

@Test
public void testSomething() {
    GreenMailUtil.sendTextEmailTest("to@localhost", "from@localhost", "subject", "body");
    MimeMessage[] emails = greenMail.getReceivedMessages();
    assertEquals(1, emails.length);
    assertEquals("subject", emails[0].getSubject());
    assertEquals("body", GreenMailUtil.getBody(emails[0]));
    // ...
}
        

Using JUnit5 extension

The JUnit5 GreenMailExtension included in com.icegreen:greenmail-junit5 replaces JUnit 4 rule GreenMailRule and also take care of starting and stopping GreenMail as part of the test lifecycle.

/** [See code on GitHub](https://github.com/greenmail-mail-test/greenmail/tree/master/greenmail-junit5/src/test/java/com/icegreen/greenmail/junit5/CustomSetupTests.java) */
@RegisterExtension
static GreenMailExtension greenMail = new GreenMailExtension(ServerSetupTest.SMTP);

@Test
@DisplayName("Send test")
void testSend() {
    GreenMailUtil.sendTextEmailTest("to@localhost", "from@localhost", "some subject", "some body");
    final MimeMessage[] receivedMessages = greenMail.getReceivedMessages();
    final MimeMessage receivedMessage = receivedMessages[0];
    assertEquals("some body", GreenMailUtil.getBody(receivedMessage));
}
        

Testing your sending code (simple)


/** [See code on GitHub](https://github.com/greenmail-mail-test/greenmail/tree/master/greenmail-core/src/test/java/com/icegreen/greenmail/examples/ExampleSendTest.java) */
GreenMail greenMail = new GreenMail(); //uses test ports by default
greenMail.start();
GreenMailUtil.sendTextEmailTest("to@localhost", "from@localhost", "some subject",
                                "some body"); // --- Place your sending code here
assertEquals("some body", GreenMailUtil.getBody(greenMail.getReceivedMessages()[0]));
greenMail.stop();
        

Testing your sending code (advanced)


/** [See code on GitHub](https://github.com/greenmail-mail-test/greenmail/tree/master/greenmail-core/src/test/java/com/icegreen/greenmail/examples/ExampleSendNoRuleAdvTest.java) */
GreenMail greenMail = new GreenMail(ServerSetupTest.ALL);
greenMail.start();

//Use random content to avoid potential residual lingering problems
final String subject = GreenMailUtil.random();
final String body = GreenMailUtil.random();

sendTestMails(subject, body); // --- Place your sending code here

//wait for max 5s for 1 email to arrive
//waitForIncomingEmail() is useful if you're sending stuff asynchronously in a separate thread
assertTrue(greenMail.waitForIncomingEmail(5000, 2));

//Retrieve using GreenMail API
Message[] messages = greenMail.getReceivedMessages();
assertEquals(2, messages.length);

// Simple message
assertEquals(subject, messages[0].getSubject());
assertEquals(body, GreenMailUtil.getBody(messages[0]).trim());

//if you send content as a 2 part multipart...
assertTrue(messages[1].getContent() instanceof MimeMultipart);
MimeMultipart mp = (MimeMultipart) messages[1].getContent();
assertEquals(2, mp.getCount());
assertEquals("body1", GreenMailUtil.getBody(mp.getBodyPart(0)).trim());
assertEquals("body2", GreenMailUtil.getBody(mp.getBodyPart(1)).trim());

greenMail.stop();
        

Testing your retrieving code


/** [See code on GitHub](https://github.com/greenmail-mail-test/greenmail/tree/master/greenmail-core/src/test/java/com/icegreen/greenmail/examples/ExampleReceiveTest.java) */
//Start all email servers using non-default ports.
GreenMail greenMail = new GreenMail(ServerSetupTest.ALL);
greenMail.start();

//Use random content to avoid potential residual lingering problems
final String subject = GreenMailUtil.random();
final String body = GreenMailUtil.random();
MimeMessage message = createMimeMessage(subject, body, greenMail); // Construct message
GreenMailUser user = greenMail.setUser("wael@localhost", "waelc", "soooosecret");
user.deliver(message);
assertEquals(1, greenMail.getReceivedMessages().length);

// --- Place your retrieve code here
greenMail.stop();
        

Testing using plain JavaMail for sending/retrieving code


/** [See code on GitHub](https://github.com/greenmail-mail-test/greenmail/tree/master/greenmail-core/src/test/java/com/icegreen/greenmail/examples/ExampleJavaMailTest.java) */
@Rule
public final GreenMailRule greenMail = new GreenMailRule(ServerSetupTest.SMTP_IMAP);

@Test
public void testSendAndReceive() throws MessagingException, ... {
    Session smtpSession = greenMail.getSmtp().createSession();

    Message msg = new MimeMessage(smtpSession);
    msg.setFrom(new InternetAddress("foo@example.com"));
    msg.addRecipient(Message.RecipientType.TO,
            new InternetAddress("bar@example.com"));
    msg.setSubject("Email sent to GreenMail via plain JavaMail");
    msg.setText("Fetch me via IMAP");
    Transport.send(msg);

    // Create user, as connect verifies pwd
    greenMail.setUser("bar@example.com", "bar@example.com", "secret-pwd");

    // Alternative 1: Create session and store or ...
    Session imapSession = greenMail.getImap().createSession();
    Store store = imapSession.getStore("imap");
    store.connect("bar@example.com", "secret-pwd");
    Folder inbox = store.getFolder("INBOX");
    inbox.open(Folder.READ_ONLY);
    Message msgReceived = inbox.getMessage(1);
    assertEquals(msg.getSubject(), msgReceived.getSubject());
    ...

    // Alternative 2: ... let GreenMail create and configure a store:
    IMAPStore imapStore = greenMail.getImap().createStore();
    imapStore.connect("bar@example.com", "secret-pwd");
    inbox = imapStore.getFolder("INBOX");
    inbox.open(Folder.READ_ONLY);
    msgReceived = inbox.getMessage(1);
    ...

    // Alternative 3: ... directly fetch sent message using GreenMail API
    assertEquals(1, greenMail.getReceivedMessagesForDomain("bar@example.com").length);
    msgReceived = greenMail.getReceivedMessagesForDomain("bar@example.com")[0];
    ...
}
        

Testing using Spring framework

The com.icegreen:greenmail-spring module provides basic support for Spring configuration via GreenMailBean:

/** See [GreenMailBeanTest.java](https://github.com/greenmail-mail-test/greenmail/tree/master/greenmail-spring/src/test/java/com/icegreen/greenmail/spring/GreenMailBeanTest.java)
 * and [GreenMailBeanTest-context.xml](greenmail-spring/src/test/resources/com/icegreen/greenmail/spring/GreenMailBeanTest-context.xml)
*/
@Autowired
private GreenMailBean greenMailBean;

@Test
public void testCreate() {
    GreenMail greenMail = greenMailBean.getGreenMail();
    ...
}
        

Deployment

Run GreenMail as standalone java application

Running GreenMail as a standalone process is useful if you want a simple sand boxed mail server.

All you require is a compatible JRE and the standalone JAR. The standalone JAR already contains all dependencies and a default logging. You can configure GreenMail by setting system properties

Starting GreenMail standalone


java [OPTIONS] -jar greenmail-standalone.jar
                
GreenMail standalone configuration options
Option Description
-Dgreenmail.setup.all Uses ServerSetup.ALL configuration to start all default mail services using default ports:
  • SMTP : 25
  • SMTPS : 465
  • IMAP : 143
  • IMAPS : 993
  • POP3 : 110
  • POP3S : 995
-Dgreenmail.setup.all
-Dgreenmail.setup.test.all Uses ServerSetupTest.ALL configuration to start all default mail services using default ports including offset of 3000:
  • SMTP : 3025
  • SMTPS : 3465
  • IMAP : 3143
  • IMAPS : 3993
  • POP3 : 3110
  • POP3S : 3995
-Dgreenmail.setup.test.all
-Dgreenmail.PROTOCOL.hostname Configures the hostname (or IP bind address) and activates a server for given protocol. Protocol can be one of
  • smtp
  • smtps
  • imap
  • imaps
  • pop3
  • pop3s
-Dgreenmail.smtp.hostname=127.0.0.1 -Dgreenmail.smtp.port=3025
-Dgreenmail.PROTOCOL.port Configures the port for given protocol. Protocol can be one of
  • smtp
  • smtps
  • imap
  • imaps
  • pop3
  • pop3s
-Dgreenmail.smtp.port=3025 -Dgreenmail.smtp.hostname=127.0.0.1
-Dgreenmail.hostname Configures the default hostname or ip bind address.
Note: Default hostname is 127.0.0.1
-Dgreenmail.smtp.port=3025 -Dgreenmail.imap.port=3143 -Dgreenmail.hostname=0.0.0.0
-Dgreenmail.users=user1[, ..., userN] Configures the user mail boxes including password.

The list of users is comma separated.

A single user is of format logon:password[@domain] , where the domain part is optional.

-Dgreenmail.users=foo:pwd@bar.com,jabber:wocky@monster.local,foo1:bar
-Dgreenmail.auth.disabled Disables user authentication check, so that any password works. Useful if you do not want to preconfigure user/passwords. GreenMail automatically creates non existent users.
Example: -Dgreenmail.auth.disabled
-Dgreenmail.verbose Enables verbose mode. Useful if you want to see debug and protocol level output.
Example: -Dgreenmail.verbose
-Dgreenmail.startup.timeout Overrides the default server startup timeout of 1000ms. Useful if you have a slow or overloaded environment.
Example with 2s startup timeout: -Dgreenmail.startup.timeout=2000
-Dlog4j.configuration

Configures log4j using given configuration file.

By default, GreenMail standalone runner uses a provided log4j configuration packed into the standalone ueber JAR. This options allows you to override the default log4j configuration by providing your own log4j configuration file.

Example: -Dlog4j.configuration=file:///tmp/log4j.xml

GreenMail standalone examples

Test setup for SMTP/IMAP and one user
Starts GreenMail for SMTP (test port 3025) and IMAP (test port 3143) using localhost/127.0.0.1 and a single user test1 with password pwd1 and email test1@localhost :

java -Dgreenmail.setup.test.smtp -Dgreenmail.setup.test.imap \
     -Dgreenmail.users=test1:pwd1 -jar greenmail-standalone.jar
                
Test setup for SMTP(S)/IMAP(S)/POP3(S) and two user
Starts GreenMail for SMTP (test port 3025), SMTPS (test port 3465), IMAP (test port 3143), IMAPS (test port 3993), POP3 (test port 3110) and POP3S (test port 3995) using localhost/127.0.0.1 :

java -Dgreenmail.setup.test.all -Dgreenmail.users=test1:pwd1,test2:pwd2@example.com \
     -jar greenmail-standalone.jar
                
Test setup for SMTP(S)/IMAP(S)/POP3(S), one user and bound to 0.0.0.0
Starts GreenMail for SMTP (test port 3025), SMTPS (test port 3465), IMAP (test port 3143), IMAPS (test port 3993), POP3 (test port 3110) and POP3S (test port 3995) using 0.0.0.0 :

java -Dgreenmail.setup.test.all -Dgreenmail.users=test1:pwd1 \
     -Dgreenmail.hostname=0.0.0.0 \
     -jar greenmail-standalone.jar
                
SMTP only
Starts GreenMail with directly configured SMTP on 127.0.0.1:4025

java -Dgreenmail.smtp.hostname=127.0.0.1 -Dgreenmail.smtp.port=4025 \
     -jar greenmail-standalone.jar
                

Deploy as a standalone Docker image

GreenMail provides a pre-configured Docker image running GreenMail standalone. The image is available via Docker Hub Public Repository, but you can also build it yourself using our Dockerfile.

By default GreenMail standalone runs using the GreenMail test setup, using the following ports (default ports plus offset of 3000):

Port Description
3025 SMTP
3110 POP3
3143 IMAP
3465 SMTPS
3993 IMAPS
3995 POP3S

Using docker to run the image


docker pull greenmail/standalone:1.6.0
docker run -t -i -p 3025:3025 -p 3110:3110 -p 3143:3143 \
                 -p 3465:3465 -p 3993:3993 -p 3995:3995 \
                 greenmail/standalone:1.6.0
                

If you want to test it, you can do a quick check with telnet (or any other mail program) by connecting to the exposed SMTP port and checking if GreenMail SMTP server responds:

Connecting with telnet to GreenMail docker SMTP service
Passing configuration options to GreenMail Standalone Docker image

You can also configure the JVM and GreenMail configuration options via the Docker environment variables JAVA_OPTS and GREENMAIL_OPTS:


docker run -t -i \
           -e GREENMAIL_OPTS='-Dgreenmail.setup.test.all -Dgreenmail.hostname=0.0.0.0 -Dgreenmail.auth.disabled -Dgreenmail.verbose' \
           -e JAVA_OPTS='-Djava.net.preferIPv4Stack=true -Xmx512m' \
           -p 3025:3025 -p 3110:3110 -p 3143:3143 \
           -p 3465:3465 -p 3993:3993 -p 3995:3995 \
           greenmail/standalone:1.5.4
                

Deploy as a webapp (WAR)

GreenMail Webapp provides a lightweight Java web application wrapping GreenMail mail server and exposing GreenMail API.

GreenMail webapp showing OpenAPI UI

The usage scenario is a development or test environment where a real mail server is too much overhead. The webapp is application server neutral - you should be able to use it on any Java EE 7 application server (Servlet 3.1) running and Java 8 (or greater).

With the GreenMail mail service each developer has its own local mail server sandbox - so there's no danger for accidentally leaking test mails into the Internet.

Deploy the webapp

Simply deploy the webapp like any other Java web application.

For Tomcat, just drop the webapp into $CATALINA_HOME/webapps directory. Alternatively, you can create a $CATALINA_HOME/webapps/greenmail, unpack the WAR here and configure the GreenMail service.

Configure the webapp

You can configure the active mail services and available users by editing WEB-INF/web.xml in the WAR file and modifying the context params. A ServletContextListener starts and stops the GreenMail service when deploying/undeploying.

Context Parameters
Name Description
greenmail.defaultHostname The mail server default hostname (defaults to localhost).
greenmail.portOffset Offset added to the standard mail ports. Default is 10000 (so an activated SMTP service would start up on port 10025).
greenmail.<PROTOCOL> Starts a server for this mail protocol (using defaultHostname, port offset and default port).

Available protocol names include

  • smtp
  • smtps (SMTP via SSL)
  • pop3
  • pop3s (POP3 via SSL)
  • imap
  • imaps (IMAP via SSL)
greenmail.<PROTOCOL>.host Optionally overwrites the default host name (localhost).
greenmail.<PROTOCOL>.port Optionally overwrites the default port and port offset for the given protocol.
greenmail.users A whitespace/newline/comma separated list of mail users in the form of USER:PWD@DOMAIN.

Have a look at the default web.xml.

FAQ

How come I don't have to create any accounts to send/retrieve?

By default GreenMail accepts all incoming emails. If there is no corresponding existing email account, one is automatically created with login and password being the same as the to-address.

What other library dependencies are there?

Check out the Maven POM. Dependencies include

  • javamail.jar and activation.jar
  • slf4j-api.jar (for logging)
  • junit.jar (for test rules)

How come I don't need to install any SSL/TLS related certificates?

GreenMail is designed to be used out of the box with no need to generate, sign or install any certificates into your keystore. GreenMail ships with a builtin keystore with a self signed RSA key. Refer to the source code of DummySSLServerSocketFactory for details.

How can I use IMAP quotas?

GreenMail supports IMAP quota. Quota capbility can be toggled on and off. For details see ImapServerTest.java quota test

How can I create or delete a mail user?


GreenMail greenMail = ...
// Create user with login id equals email
GreenMailUser user1 = greenMail.setUser("foo@localhost", "some secret pwd");
// Create user with login id different than email
GreenMailUser user2 = greenMail.setUser("foo@localhost", "login-id", "some secret pwd");
...
greenMail.getManagers().getUserManager().deleteUser(user1); // Delete user

How can I get more verbose output?

Enable the verbose mode, which prints debug output and protocol level communication.
See ServerSetup.setVerbose(boolean) or GreenMail standalone runner option greenmail.verbose option.

Example of activating verbose mode when configuring via GreenMailRule:


@Rule
public final GreenMailRule greenMail = new GreenMailRule(ServerSetup.verbose(ServerSetupTest.SMTP_IMAP));

Download

Maven Central contains all GreenMail artifacts.

Docker images are availalbe on Docker Hub GreenMail Repository, such as for the GreenMail standalone runner.

1.6.0 - August 16th, 2020

Name GAV
GreenMail Core com.icegreen:greenmail:1.6.0
GreenMail Standalone com.icegreen:greenmail-standalone:1.6.0 (Docker Hub)
GreenMail Webapp com.icegreen:greenmail-webapp:1.6.0:war
GreenMail Spring com.icegreen:greenmail-spring:1.6.0

Available via Maven repository or as a ZIP from GitHub.

1.5.14 - July 4th, 2020

Name GAV
GreenMail Core com.icegreen:greenmail:1.5.14
GreenMail Standalone com.icegreen:greenmail-standalone:1.5.14 (Docker Hub)
GreenMail Webapp com.icegreen:greenmail-webapp:1.5.14:war
GreenMail JBoss Service com.icegreen:greenmail-jboss-service:1.5.14:jboss-sar
GreenMail Spring com.icegreen:greenmail-spring:1.5.14

Available via Maven repository or as a ZIP from GitHub.

1.5.11 - Oct 22, 2019

Name GAV
GreenMail Core com.icegreen:greenmail:1.5.11
GreenMail Standalone com.icegreen:greenmail-standalone:1.5.11 (Docker Hub)
GreenMail Webapp com.icegreen:greenmail-webapp:1.5.11:war
GreenMail JBoss Service com.icegreen:greenmail-jboss-service:1.5.11:jboss-sar
GreenMail Spring com.icegreen:greenmail-spring:1.5.11

Available via Maven repository or as a ZIP from GitHub.

1.4.1 - April 27th, 2015

Name GAV
GreenMail Core com.icegreen:greenmail:1.4.1
GreenMail Webapp com.icegreen:greenmail-webapp:1.4.1:war
GreenMail JBoss Service com.icegreen:greenmail-jboss-service:1.4.1:jboss-sar
GreenMail Spring com.icegreen:greenmail-spring:1.4.1

Download bundle as ZIP from GitHub.

1.3.1b - June 14th 2009

This version runs on JDK 1.4+ and JavaMail 1.4 .
Name GAV
GreenMail Core com.icegreen:greenmail:1.3.1b
GreenMail JBoss Service com.icegreen:greenmail-jboss-service:1.3.1b:jboss-sar

Older versions

You can find older version at the old SourceForge download section