Package com.sun.mail.pop3

See:
          Description

Package com.sun.mail.pop3 Description

The POP3 provider provides a Store object that contains a single Folder named "INBOX". Due to the limitations of the POP3 protocol, many of the JavaMail API capabilities like event notification, folder management, flag management, etc. are not allowed. The corresponding methods throw the MethodNotSupportedException exception; see below for details.

Note that JavaMail does not include a local store into which messages can be downloaded and stored. See our Third Party Products web page for availability of "mbox" and "MH" local store providers.

The POP3 provider is accessed through the JavaMail APIs by using the protocol name "pop3" or a URL of the form "pop3://user:password@host:port/INBOX".

POP3 supports only a single folder named "INBOX".

POP3 supports no permanent flags (see {@link javax.mail.Folder#getPermanentFlags Folder.getPermanentFlags()}). In particular, the Flags.Flag.RECENT flag will never be set for POP3 messages. It's up to the application to determine which messages in a POP3 mailbox are "new". There are several strategies to accomplish this, depending on the needs of the application and the environment:

• A simple approach would be to keep track of the newest message seen by the application.
• An alternative would be to keep track of the UIDs (see below) of all messages that have been seen.
• Another approach is to download all messages into a local mailbox, so that all messages in the POP3 mailbox are, by definition, new.

All approaches will require some permanent storage associated with the client.

POP3 does not support the Folder.expunge() method. To delete and expunge messages, set the Flags.Flag.DELETED flag on the messages and close the folder using the Folder.close(true) method. You cannot expunge without closing the folder.

POP3 does not provide a "received date", so the getReceivedDate method will return null. It may be possible to examine other message headers (e.g., the "Received" headers) to estimate the received date, but these techniques are error-prone at best.

The POP3 provider supports the POP3 UIDL command, see {@link com.sun.mail.pop3.POP3Folder#getUID POP3Folder.getUID()}. You can use it as follows:

if (folder instanceof com.sun.mail.pop3.POP3Folder) {
    com.sun.mail.pop3.POP3Folder pf =
	(com.sun.mail.pop3.POP3Folder)folder;
    String uid = pf.getUID(msg);
    if (uid != null)
	... // use it
}

You can also pre-fetch all the UIDs for all messages like this:

FetchProfile fp = new FetchProfile();
fp.add(UIDFolder.FetchProfileItem.UID);
folder.fetch(folder.getMessages(), fp);

Then use the technique above to get the UID for each message. This is similar to the technique used with the UIDFolder interface supported by IMAP, but note that POP3 UIDs are strings, not integers like IMAP UIDs. See the POP3 spec for details.

The POP3 protocol provider supports the following properties, which may be set in the JavaMail Session object. The properties are always set as strings; the Type column describes how the string is interpreted. For example, use

	props.put("mail.pop3.port", "888");

In general, applications should not need to use the classes in this package directly. Instead, they should use the APIs defined by javax.mail package (and subpackages). Applications should never construct instances of POP3Store or POP3Folder directly. Instead, they should use the Session method getStore to acquire an appropriate Store object, and from that acquire Folder objects.

WARNING: The APIs unique to this package should be considered EXPERIMENTAL. They may be changed in the future in ways that are incompatible with applications using the current APIs.