An IMAP protocol provider for the Jakarta Mail API that provides access to an IMAP message store. Both the IMAP4 and IMAP4rev1 protocols are supported. Refer to RFC 3501 for more information. The IMAP protocol provider also supports many IMAP extensions (described below). Note that the server needs to support these extensions (and not all servers do) in order to use the support in the IMAP provider. You can query the server for support of these extensions using the {@link com.sun.mail.imap.IMAPStore#hasCapability IMAPStore hasCapability} method using the capability name defined by the extension (see the appropriate RFC) after connecting to the server.

UIDPLUS Support

The IMAP UIDPLUS extension (RFC 4315) is supported via the IMAPFolder methods {@link com.sun.mail.imap.IMAPFolder#addMessages addMessages}, {@link com.sun.mail.imap.IMAPFolder#appendUIDMessages appendUIDMessages}, and {@link com.sun.mail.imap.IMAPFolder#copyUIDMessages copyUIDMessages}.

MOVE Support

The IMAP MOVE extension (RFC 6851) is supported via the IMAPFolder methods {@link com.sun.mail.imap.IMAPFolder#moveMessages moveMessages} and {@link com.sun.mail.imap.IMAPFolder#moveUIDMessages moveUIDMessages}.

SASL Support

The IMAP protocol provider can use SASL (RFC 4422) authentication mechanisms on systems that support the `javax.security.sasl` APIs. The SASL-IR (RFC 4959) capability is also supported. In addition to the SASL mechanisms that are built into the SASL implementation, users can also provide additional SASL mechanisms of their own design to support custom authentication schemes. See the Java SASL API Programming and Deployment Guide for details. Note that the current implementation doesn't support SASL mechanisms that provide their own integrity or confidentiality layer.

OAuth 2.0 Support

Support for OAuth 2.0 authentication via the XOAUTH2 authentication mechanism is provided either through the SASL support described above or as a built-in authentication mechanism in the IMAP provider. The OAuth 2.0 Access Token should be passed as the password for this mechanism. See OAuth2 Support for details.

Connection Pool

A connected IMAPStore maintains a pool of IMAP protocol objects for use in communicating with the IMAP server. The IMAPStore will create the initial AUTHENTICATED connection and seed the pool with this connection. As folders are opened and new IMAP protocol objects are needed, the IMAPStore will provide them from the connection pool, or create them if none are available. When a folder is closed, its IMAP protocol object is returned to the connection pool if the pool is not over capacity.

A mechanism is provided for timing out idle connection pool IMAP protocol objects. Timed out connections are closed and removed (pruned) from the connection pool.

The connected IMAPStore object may or may not maintain a separate IMAP protocol object that provides the store a dedicated connection to the IMAP server. This is provided mainly for compatibility with previous implementations of the IMAP protocol provider.

QUOTA Support

The IMAP QUOTA extension (RFC 2087) is supported via the {@link javax.mail.QuotaAwareStore QuotaAwareStore} interface implemented by {@link com.sun.mail.imap.IMAPStore IMAPStore}, and the {@link com.sun.mail.imap.IMAPFolder#getQuota IMAPFolder getQuota} and {@link com.sun.mail.imap.IMAPFolder#setQuota IMAPFolder setQuota} methods. ACL Support

The IMAP ACL extension (RFC 2086) is supported via the {@link com.sun.mail.imap.Rights Rights} class and the IMAPFolder methods {@link com.sun.mail.imap.IMAPFolder#getACL getACL}, {@link com.sun.mail.imap.IMAPFolder#addACL addACL}, {@link com.sun.mail.imap.IMAPFolder#removeACL removeACL}, {@link com.sun.mail.imap.IMAPFolder#addRights addRights}, {@link com.sun.mail.imap.IMAPFolder#removeRights removeRights}, {@link com.sun.mail.imap.IMAPFolder#listRights listRights}, and {@link com.sun.mail.imap.IMAPFolder#myRights myRights}.

SORT Support

The IMAP SORT extension (RFC 5256) is supported via the {@link com.sun.mail.imap.SortTerm SortTerm} class and the IMAPFolder {@link com.sun.mail.imap.IMAPFolder#getSortedMessages getSortedMessages} methods.

CONDSTORE and QRESYNC Support

Basic support is provided for the IMAP CONDSTORE (RFC 4551) and QRESYNC (RFC 5162) extensions for the purpose of resynchronizing a folder after offline operation. Of course, the server must support these extensions. Use of these extensions is enabled by using the new {@link com.sun.mail.imap.IMAPFolder#open(int,com.sun.mail.imap.ResyncData) IMAPFolder open} method and supplying an appropriate {@link com.sun.mail.imap.ResyncData ResyncData} instance. Using {@link com.sun.mail.imap.ResyncData#CONDSTORE ResyncData.CONDSTORE} enables the CONDSTORE extension, which allows you to discover the modification sequence number (modseq) of messages using the {@link com.sun.mail.imap.IMAPMessage#getModSeq IMAPMessage getModSeq} method and the {@link com.sun.mail.imap.IMAPFolder#getHighestModSeq IMAPFolder getHighestModSeq} method. Using a {@link com.sun.mail.imap.ResyncData ResyncData} instance with appropriate values also allows the server to report any changes in messages since the last resynchronization. The changes are reported as a list of {@link javax.mail.event.MailEvent MailEvent} instances. The special {@link com.sun.mail.imap.MessageVanishedEvent MessageVanishedEvent} reports on UIDs of messages that have been removed since the last resynchronization. A {@link javax.mail.event.MessageChangedEvent MessageChangedEvent} reports on changes to flags of messages. For example:

    	Folder folder = store.getFolder("whatever");
    	IMAPFolder ifolder = (IMAPFolder)folder;
    	List<MailEvent> events = ifolder.open(Folder.READ_WRITE,
    		    new ResyncData(prevUidValidity, prevModSeq));
    	for (MailEvent ev : events) {
    	    if (ev instanceOf MessageChangedEvent) {
    		// process flag changes
    	    } else if (ev instanceof MessageVanishedEvent) {
    		// process messages that were removed
    	    }
    	}

See the referenced RFCs for more details on these IMAP extensions.

WITHIN Search Support

The IMAP WITHIN search extension (RFC 5032) is supported via the {@link com.sun.mail.imap.YoungerTerm YoungerTerm} and {@link com.sun.mail.imap.OlderTerm OlderTerm} {@link javax.mail.search.SearchTerm SearchTerms}, which can be used as follows:

    	// search for messages delivered in the last day
    	Message[] msgs = folder.search(new YoungerTerm(24 * 60 * 60));

LOGIN-REFERRAL Support

The IMAP LOGIN-REFERRAL extension (RFC 2221) is supported. If a login referral is received when connecting or when authentication fails, a {@link com.sun.mail.imap.ReferralException ReferralException} is thrown. A referral can also occur when login succeeds. By default, no exception is thrown in this case. To force an exception to be thrown and the authentication to fail, set the `mail.imap.referralexception` property to "true".

COMPRESS Support

The IMAP COMPRESS extension (RFC 4978) is supported. If the server supports the extension and the `mail.imap.compress.enable` property is set to "true", compression will be enabled.

UTF-8 Support

The IMAP UTF8 extension (RFC 6855) is supported. If the server supports the extension, the client will enable use of UTF-8, allowing use of UTF-8 in IMAP protocol strings such as folder names.

Properties

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

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

to set the `mail.imap.port` property, which is of type int.

Note that if you're using the "imaps" protocol to access IMAP over SSL, all the properties would be named "mail.imaps.*".

IMAP properties
Name | Type | Description
--- | --- | ---
mail.imap.user | String | Default user name for IMAP.
mail.imap.host | String | The IMAP server to connect to.
mail.imap.port | int | The IMAP server port to connect to, if the connect() method doesn't explicitly specify one. Defaults to 143.
mail.imap.partialfetch | boolean | Controls whether the IMAP partial-fetch capability should be used. Defaults to true.
mail.imap.fetchsize | int | Partial fetch size in bytes. Defaults to 16K.
mail.imap.peek | boolean | If set to true, use the IMAP PEEK option when fetching body parts, to avoid setting the SEEN flag on messages. Defaults to false. Can be overridden on a per-message basis by the {@link com.sun.mail.imap.IMAPMessage#setPeek setPeek} method on IMAPMessage.
mail.imap.ignorebodystructuresize | boolean | The IMAP BODYSTRUCTURE response includes the exact size of each body part. Normally, this size is used to determine how much data to fetch for each body part. Some servers report this size incorrectly in some cases; this property can be set to work around such server bugs. If this property is set to true, this size is ignored and data is fetched until the server reports the end of data. This will result in an extra fetch if the data size is a multiple of the block size. Defaults to false.
mail.imap.connectiontimeout | int | Socket connection timeout value in milliseconds. This timeout is implemented by java.net.Socket. Default is infinite timeout.
mail.imap.timeout | int | Socket read timeout value in milliseconds. This timeout is implemented by java.net.Socket. Default is infinite timeout.
mail.imap.writetimeout | int | Socket write timeout value in milliseconds. This timeout is implemented by using a java.util.concurrent.ScheduledExecutorService per connection that schedules a thread to close the socket if the timeout expires. Thus, the overhead of using this timeout is one thread per connection. Default is infinite timeout.
mail.imap.statuscachetimeout | int | Timeout value in milliseconds for cache of STATUS command response. Default is 1000 (1 second). Zero disables cache.
mail.imap.appendbuffersize | int | Maximum size of a message to buffer in memory when appending to an IMAP folder. If not set, or set to -1, there is no maximum and all messages are buffered. If set to 0, no messages are buffered. If set to (e.g.) 8192, messages of 8K bytes or less are buffered, larger messages are not buffered. Buffering saves cpu time at the expense of short term memory usage. If you commonly append very large messages to IMAP mailboxes you might want to set this to a moderate value (1M or less).
mail.imap.connectionpoolsize | int | Maximum number of available connections in the connection pool. Default is 1.
mail.imap.connectionpooltimeout | int | Timeout value in milliseconds for connection pool connections. Default is 45000 (45 seconds).
mail.imap.separatestoreconnection | boolean | Flag to indicate whether to use a dedicated store connection for store commands. Default is false.
mail.imap.allowreadonlyselect | boolean | If false, attempts to open a folder read/write will fail if the SELECT command succeeds but indicates that the folder is READ-ONLY. This sometimes indicates that the folder contents can'tbe changed, but the flags are per-user and can be changed, such as might be the case for public shared folders. If true, such open attempts will succeed, allowing the flags to be changed. The `getMode` method on the `Folder` object will return `Folder.READ_ONLY` in this case even though the `open` method specified `Folder.READ_WRITE`. Default is false.
mail.imap.auth.mechanisms | String | If set, lists the authentication mechanisms to consider, and the order in which to consider them. Only mechanisms supported by the server and supported by the current implementation will be used. The default is `"PLAIN LOGIN NTLM"`, which includes all the authentication mechanisms supported by the current implementation except XOAUTH2.
mail.imap.auth.login.disable | boolean | If true, prevents use of the non-standard `AUTHENTICATE LOGIN` command, instead using the plain `LOGIN` command. Default is false.
mail.imap.auth.plain.disable | boolean | If true, prevents use of the `AUTHENTICATE PLAIN` command. Default is false.
mail.imap.auth.ntlm.disable | boolean | If true, prevents use of the `AUTHENTICATE NTLM` command. Default is false.
mail.imap.auth.ntlm.domain | String | The NTLM authentication domain.
mail.imap.auth.ntlm.flags | int | NTLM protocol-specific flags. See http://curl.haxx.se/rfc/ntlm.html#theNtlmFlags for details.
mail.imap.auth.xoauth2.disable | boolean | If true, prevents use of the `AUTHENTICATE XOAUTH2` command. Because the OAuth 2.0 protocol requires a special access token instead of a password, this mechanism is disabled by default. Enable it by explicitly setting this property to "false" or by setting the "mail.imap.auth.mechanisms" property to "XOAUTH2".
mail.imap.proxyauth.user | String | If the server supports the PROXYAUTH extension, this property specifies the name of the user to act as. Authenticate to the server using the administrator's credentials. After authentication, the IMAP provider will issue the `PROXYAUTH` command with the user name specified in this property.
mail.imap.localaddress | String | Local address (host name) to bind to when creating the IMAP socket. Defaults to the address picked by the Socket class. Should not normally need to be set, but useful with multi-homed hosts where it's important to pick a particular local address to bind to.
mail.imap.localport | int | Local port number to bind to when creating the IMAP socket. Defaults to the port number picked by the Socket class.
mail.imap.sasl.enable | boolean | If set to true, attempt to use the javax.security.sasl package to choose an authentication mechanism for login. Defaults to false.
mail.imap.sasl.mechanisms | String | A space or comma separated list of SASL mechanism names to try to use.
mail.imap.sasl.authorizationid | String | The authorization ID to use in the SASL authentication. If not set, the authentication ID (user name) is used.
mail.imap.sasl.realm | String | The realm to use with SASL authentication mechanisms that require a realm, such as DIGEST-MD5.
mail.imap.sasl.usecanonicalhostname | boolean | If set to true, the canonical host name returned by {@link java.net.InetAddress#getCanonicalHostName InetAddress.getCanonicalHostName} is passed to the SASL mechanism, instead of the host name used to connect. Defaults to false.
mail.imap.sasl. xgwtrustedapphack.enable | boolean | If set to true, enables a workaround for a bug in the Novell Groupwise XGWTRUSTEDAPP SASL mechanism, when that mechanism is being used. Defaults to true.
mail.imap.socketFactory | SocketFactory | If set to a class that implements the `javax.net.SocketFactory` interface, this class will be used to create IMAP sockets. Note that this is an instance of a class, not a name, and must be set using the `put` method, not the `setProperty` method.
mail.imap.socketFactory.class | String | If set, specifies the name of a class that implements the `javax.net.SocketFactory` interface. This class will be used to create IMAP sockets.
mail.imap.socketFactory.fallback | boolean | If set to true, failure to create a socket using the specified socket factory class will cause the socket to be created using the `java.net.Socket` class. Defaults to true.
mail.imap.socketFactory.port | int | Specifies the port to connect to when using the specified socket factory. If not set, the default port will be used.
mail.imap.usesocketchannels | boolean | If set to true, use SocketChannels instead of Sockets for connecting to the server. Required if using the IdleManager. Ignored if a socket factory is set. Defaults to false.
mail.imap.ssl.enable | boolean | If set to true, use SSL to connect and use the SSL port by default. Defaults to false for the "imap" protocol and true for the "imaps" protocol.
mail.imap.ssl.checkserveridentity | boolean | If set to true, check the server identity as specified by RFC 2595. These additional checks based on the content of the server's certificate are intended to prevent man-in-the-middle attacks. Defaults to false.
mail.imap.ssl.trust | String | If set, and a socket factory hasn't been specified, enables use of a {@link com.sun.mail.util.MailSSLSocketFactory MailSSLSocketFactory}. If set to "*", all hosts are trusted. If set to a whitespace separated list of hosts, those hosts are trusted. Otherwise, trust depends on the certificate the server presents.
mail.imap.ssl.socketFactory | SSLSocketFactory | If set to a class that extends the `javax.net.ssl.SSLSocketFactory` class, this class will be used to create IMAP SSL sockets. Note that this is an instance of a class, not a name, and must be set using the `put` method, not the `setProperty` method.
mail.imap.ssl.socketFactory.class | String | If set, specifies the name of a class that extends the `javax.net.ssl.SSLSocketFactory` class. This class will be used to create IMAP SSL sockets.
mail.imap.ssl.socketFactory.port | int | Specifies the port to connect to when using the specified socket factory. If not set, the default port will be used.
mail.imap.ssl.protocols | string | Specifies the SSL protocols that will be enabled for SSL connections. The property value is a whitespace separated list of tokens acceptable to the `javax.net.ssl.SSLSocket.setEnabledProtocols` method.
mail.imap.ssl.ciphersuites | string | Specifies the SSL cipher suites that will be enabled for SSL connections. The property value is a whitespace separated list of tokens acceptable to the `javax.net.ssl.SSLSocket.setEnabledCipherSuites` method.
mail.imap.starttls.enable | boolean | If true, enables the use of the `STARTTLS` command (if supported by the server) to switch the connection to a TLS-protected connection before issuing any login commands. If the server does not support STARTTLS, the connection continues without the use of TLS; see the `mail.imap.starttls.required` property to fail if STARTTLS isn't supported. Note that an appropriate trust store must configured so that the client will trust the server's certificate. Default is false.
mail.imap.starttls.required | boolean | If true, requires the use of the `STARTTLS` command. If the server doesn't support the STARTTLS command, or the command fails, the connect method will fail. Defaults to false.
mail.imap.proxy.host | string | Specifies the host name of an HTTP web proxy server that will be used for connections to the mail server.
mail.imap.proxy.port | string | Specifies the port number for the HTTP web proxy server. Defaults to port 80.
mail.imap.proxy.user | string | Specifies the user name to use to authenticate with the HTTP web proxy server. By default, no authentication is done.
mail.imap.proxy.password | string | Specifies the password to use to authenticate with the HTTP web proxy server. By default, no authentication is done.
mail.imap.socks.host | string | Specifies the host name of a SOCKS5 proxy server that will be used for connections to the mail server.
mail.imap.socks.port | string | Specifies the port number for the SOCKS5 proxy server. This should only need to be used if the proxy server is not using the standard port number of 1080.
mail.imap.minidletime | int | Applications typically call the idle method in a loop. If another thread termiantes the IDLE command, it needs a chance to do its work before another IDLE command is issued. The idle method enforces a delay to prevent thrashing between the IDLE command and regular commands. This property sets the delay in milliseconds. If not set, the default is 10 milliseconds.
mail.imap.enableresponseevents | boolean | Enable special IMAP-specific events to be delivered to the Store's `ConnectionListener`. If true, IMAP OK, NO, BAD, or BYE responses will be sent as `ConnectionEvent`s with a type of `IMAPStore.RESPONSE`. The event's message will be the raw IMAP response string. By default, these events are not sent. NOTE: This capability is highly experimental and likely will change in future releases.
mail.imap.enableimapevents | boolean | Enable special IMAP-specific events to be delivered to the Store's `ConnectionListener`. If true, unsolicited responses received during the Store's `idle` method will be sent as `ConnectionEvent`s with a type of `IMAPStore.RESPONSE`. The event's message will be the raw IMAP response string. By default, these events are not sent. NOTE: This capability is highly experimental and likely will change in future releases.
mail.imap.throwsearchexception | boolean | If set to true and a {@link javax.mail.search.SearchTerm SearchTerm} passed to the {@link javax.mail.Folder#search Folder.search} method is too complex for the IMAP protocol, throw a {@link javax.mail.search.SearchException SearchException}. For example, the IMAP protocol only supports less-than and greater-than comparisons for a {@link javax.mail.search.SizeTerm SizeTerm}. If false, the search will be done locally by fetching the required message data and comparing it locally. Defaults to false.
mail.imap.folder.class | String | Class name of a subclass of `com.sun.mail.imap.IMAPFolder`. The subclass can be used to provide support for additional IMAP commands. The subclass must have public constructors of the form `public MyIMAPFolder(String fullName, char separator, IMAPStore store, Boolean isNamespace)` and `public MyIMAPFolder(ListInfo li, IMAPStore store)`
mail.imap.closefoldersonstorefailure | boolean | In some cases, a failure of the Store connection indicates a failure of the server, and all Folders associated with that Store should also be closed. In other cases, a Store connection failure may be a transient failure, and Folders may continue to operate normally. If this property is true (the default), failures in the Store connection cause all associated Folders to be closed. Set this property to false to better handle transient failures in the Store connection.
mail.imap.finalizecleanclose | boolean | When the finalizer for IMAPStore is called, should the connection to the server be closed cleanly, as if the application called the close method? Or should the connection to the server be closed without sending any commands to the server? Defaults to false, the connection is not closed cleanly.
mail.imap.referralexception | boolean | If set to true and an IMAP login referral is returned when the authentication succeeds, fail the connect request and throw a {@link com.sun.mail.imap.ReferralException ReferralException}. Defaults to false.
mail.imap.compress.enable | boolean | If set to true and the IMAP server supports the COMPRESS=DEFLATE extension, compression will be enabled. Defaults to false.
mail.imap.compress.level | int | The compression level to be used, in the range -1 to 9. See the {@link java.util.zip.Deflater Deflater} class for details.
mail.imap.compress.strategy | int | The compression strategy to be used, in the range 0 to 2. See the {@link java.util.zip.Deflater Deflater} class for details.
mail.imap.reusetagprefix | boolean | If true, always use "A" for the IMAP command tag prefix. If false, the IMAP command tag prefix is different for each connection, from "A" through "ZZZ" and then wrapping around to "A". Applications should never need to set this. Defaults to false.

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

Loggers

In addition to printing debugging output as controlled by the {@link javax.mail.Session Session} configuration, the com.sun.mail.imap provider logs the same information using {@link java.util.logging.Logger} as described in the following table:

IMAP Loggers
Logger Name | Logging Level | Purpose
--- | --- | ---
com.sun.mail.imap | CONFIG | Configuration of the IMAPStore
com.sun.mail.imap | FINE | General debugging output
com.sun.mail.imap.connectionpool | CONFIG | Configuration of the IMAP connection pool
com.sun.mail.imap.connectionpool | FINE | Debugging output related to the IMAP connection pool
com.sun.mail.imap.messagecache | CONFIG | Configuration of the IMAP message cache
com.sun.mail.imap.messagecache | FINE | Debugging output related to the IMAP message cache
com.sun.mail.imap.protocol | FINEST | Complete protocol trace

WARNING

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.