Serializing Java MimeMessage

Why doesn't the MimeMessage class implement Serializable so that I can serialize a message to disk and read it back later?

The JavaMail API was designed to layer on top of existing email systems, using existing message formats. The ability to use Java serialization was neither essential nor useful for such implementations, and thus was not considered a goal of the JavaMail API.

The hard part about serializing a Message is retaining the pointers to the Folder, Store and Session. If you only want to save the content of the message, and not the object itself, the writeTo method of a message gives your everything you need. If you want to create an entire email system based on serialized messages, you should be able to subclass Message et. al and implement Serializable in your subclass.

If you want to serialize other objects of your own that reference MimeMessages, the writeObject method of your object can use the writeTo method of MimeMessage, and the readObject method of your object can use the MimeMessage constructore that takes an InputStream. Your class will need to provide a Session when constructing the MimeMessage.