About Mail4ME

Mail4ME is a lightweight implementation of the popular POP3, IMAP and SMTP protocols - including MIME support - allowing wireless J2ME/MIDP devices to access the Internet e-mail service at any time, and from any place (as long as a suitable antenna is in reach and the device's battery is not empty, of course).

Since the project targets the J2ME environment, the implementation has to respect the limited resources available there. In particular this implies that it's not possible to represent every tiny piece of information an e-mail contains or may contain by a specilized Java class, so the level of abstraction is somewhat lower than the one used by JavaMail.

The basic concepts of the implementation look like this:

Protocols are encapsulated by one class each, so we have a Pop3Client class, an ImapClient class and an SmtpClient class for the various protocols as well as a MailException class to report errors during sessions. To make run-time selection of protocols easy for application programmers, both Pop3Client and ImapClient implement the interface .
A Message is represented by a line-oriented data structure encapsulated in a class with exactly that name, basically separating the header and body parts. This representation is easy to implement as well as easy to use, and it requires little memory. It's also very close to the data format that is used during actual transmission, so there's not much transformation needed, which makes it reasonably fast even on the typically not-so-fast J2ME devices.
A special MimeDecoder class allows to access to the tree-like hierarchy of body parts in a MIME-encoded message.
Since the implementation uses a helper class that abstracts from J2ME's Generic Connection Framework as well as from J2SE's Socket class, the package can be used in both environments, thus presenting a tiny alternative to JavaMail even for the desktop.

The diagram below sketches the basic relationships between the various core classes contained in the package.