Java Enterprise Best Practices

Choose an Effective Delivery Mechanism

Because JavaMail doesn’t provide any provision for having mail delivered to an application, there is an architectural decision to be made regarding how incoming messages will be retrieved. In practice, this comes down to deciding whether you want to retrieve messages from an IMAP mailbox or a POP3 mailbox. In some environments this decision will be made for you, but when possible, it’s helpful to evaluate the two options.

POP3 has the advantage of simplicity. It’s almost impossible to find a mail server that doesn’t support POP, and implementations are very mature. The protocol itself is older and is geared toward listing, retrieving, and deleting messages from a single, undifferentiated pool. For simple process flows, such as when one mailbox is dedicated to a particular application and the application deletes messages after retrieving them, POP is generally the best choice.

POP falls short when dealing with complex message stores. It has no support for folders, no query system, and minimal support for downloading parts of messages. This is where IMAP comes in. Like POP, IMAP allows clients to connect to remote message stores. However, while POP assumes that the client will download messages and store them locally, IMAP assumes that messages will be stored on the server and provides support for multiple mailbox folders to aid in organization. More advanced IMAP implementations can provide a degree of write access to the contents of the message ...