Factory
Interfaces, Classes and Traits
- MessagePartFactory
 - Abstract factory for subclasses of MessagePart.
 - MimePartFactory
 - Responsible for creating MimePart instances.
 - NonMimePartFactory
 - Responsible for creating NoneMimePart instances.
 - PartBuilderFactory
 - Responsible for creating PartBuilder instances.
 - PartFactoryService
 - Responsible for creating singleton instances of MessagePartFactory and its subclasses.
 - PartStreamFilterManagerFactory
 - Responsible for creating PartStreamFilterManager instances.
 - UUEncodedPartFactory
 - Responsible for creating UUEncodedPart instances.