Building

To build you will need:

• J2SE SDK 1.8+
• Maven 3.9.x

To build all changes incrementally:

mvn install

To perform clean builds, which are sometimes needed after some changes to the source tree:

mvn clean install

SSL/TLS Protocols used for Mail Connection

Default Behaviour

By default, the implementation checks for the presence of ssl.protocols. If this property is not set, the SSL/TLS socket is created with JVM defaults.

Enable Custom SSL Protocols

The property ssl.protocols can be used to specify a list of protocols, which should be enabled for the underlying SSL/TLS socket. It accepts a list of protocols with a whitespace as delimiter.

Example for SMTP

To support TLSv1+ the following property can be set:

mail.smtp.ssl.protocols=TLSv1 TLSv1.1 TLSv1.2 TLSv1.3
``

## Using a Custom SSL Socket Factory (via Reflection)

The property `ssl.socketFactory.class` can be used to specify a custom SSL socket factory, which is used to create the underlying SSL/TLS socket.
This allows full control of supported cyphers or protocols.

#### Example for SMTP

mail.smtp.ssl.socketFactory.class=my.custom.CustomSSLSocketFactory ``

Using a Custom SSL Socket Factory (as pre-configured instance)

The property ssl.socketFactory can be used to specify a pre-configured custom SSL socket factory, which is used to create the underlying SSL/TLS socket. In this context, the instance has to be passed to the Properties of the related MailSession. This allows full control of supported cyphers or protocols.

Cipher suites

Default Behaviour

By default, the implementation checks for the presence of ssl.ciphersuites. If this property is not set, the SSL/TLS socket is created with all supported ciphers of the given SSL Socket.

Enable Custom Cipher Suites

The property ssl.ciphersuites can be used to specify a list of ciphers, which should be enabled for the underlying SSL/TLS socket. It accepts a list of ciphers with a whitespace as delimiter. You have to ensure, that the listed cipher suites are supported by the given JVM.

Example for SMTP

To support only TLS_AES_128_GCM_SHA256 and TLS_AES_256_GCM_SHA384 the following property can be set:

mail.smtp.ssl.ciphersuites=TLS_AES_128_GCM_SHA256 TLS_AES_256_GCM_SHA384
``

## Using a Custom SSL Socket Factory (via Reflection)

The property `ssl.socketFactory.class` can be used to specify a custom SSL socket factory, which is used to create the underlying SSL/TLS socket.
This allows full control of supported cyphers or protocols.

#### Example for SMTP

mail.smtp.ssl.socketFactory.class=my.custom.CustomSSLSocketFactory ``

Using a Custom SSL Socket Factory (as pre-configured instance)

The property ssl.socketFactory can be used to specify a pre-configured custom SSL socket factory, which is used to create the underlying SSL/TLS socket. In this context, the instance has to be passed to the Properties of the related MailSession. This allows full control of supported cyphers or protocols.