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Mail::Transport::IMAP4 - proxy to Mail::IMAPClient


   is a Mail::Transport::Receive
   is a Mail::Transport
   is a Mail::Reporter


 my $imap = Mail::Transport::IMAP4->new(...);
 my $message = $imap->receive($id);

 my Mail::Box::Manager $mgr = Mail::Box::Manager->new;
     # Generic folder options
     folder => 'imaps://...',
     access => 'rw',
     extract => 'ALWAYS',

     # Mail::IMAPClient options start with [A-Z]
     IgnoreSizeErrors => 1,
     Ssl => 1,


The IMAP4 protocol is quite complicated: it is feature rich and allows various asynchronous actions. The main document describing IMAP is rfc3501 (which obsoleted the original specification of protocol 4r1 in rfc2060 in March 2003).

This package, as part of MailBox, does not implement the actual protocol itself but uses Mail::IMAPClient to do the work. The task for this package is to hide as many differences between that module's interface and the common MailBox folder types. Multiple Mail::Box::IMAP4 folders can share one Mail::Transport::IMAP4 connection.

The Mail::IMAPClient module is the best IMAP4 implementation for Perl5, but is not maintained. There are many known problems with the module, and solving those is outside the scope of MailBox. See for all the reported bugs.

Extends "DESCRIPTION" in Mail::Transport::Receive.


Extends "METHODS" in Mail::Transport::Receive.


Extends "Constructors" in Mail::Transport::Receive.


Create the IMAP connection to the server. IMAP servers can handle multiple folders for a single user, which means that connections may get shared. This is sharing is hidden for the user.

When an imap_client is specified, then the options hostname, port, username, and password are extracted from it.

All %options which start with a capital are passed as initiation to Mail::IMAPClient. See that manual about the huge pile of parameters. When talking to Microsoft Exchange, you probabaly need the IgnoreSizeErros. Probably, you need Ssl or StartTLS as well. As feature, you may also pass a HASH to Ssl, where Mail::IMAPClient only accepts an ARRAY.

For backwards compatibility, ssl is an alternative for Ssl, and starttls for StartTLS.

 -Option      --Defined in     --Default
  authenticate                   'AUTO'
  domain                         <server_name>
  executable    Mail::Transport  undef
  hostname      Mail::Transport  'localhost'
  imap_client                    Mail::IMAPClient
  interval      Mail::Transport  30
  log           Mail::Reporter   'WARNINGS'
  password      Mail::Transport  undef
  port          Mail::Transport  143
  proxy         Mail::Transport  undef
  retry         Mail::Transport  <false>
  timeout       Mail::Transport  120
  trace         Mail::Reporter   'WARNINGS'
  username      Mail::Transport  undef
  via           Mail::Transport  'imap'
authenticate => TYPE|ARRAY

Authenthication method to login(), which will be passed to Mail::IMAPClient subroutine authenticate. See the latter method for the available types. You may provide an ARRAY of types.


Used for NTLM authentication.

executable => FILENAME
hostname => HOSTNAME|ARRAY
imap_client => OBJECT|CLASS

When an OBJECT is supplied, that client will be used for the implementation of the IMAP4 protocol. Information about server and such are extracted from the OBJECT to have the accessors to produce correct results. The OBJECT shall be a Mail::IMAPClient.

When a CLASS is given, an object of that type is created for you. The created object can be retrieved via imapClient(), and than configured as defined by Mail::IMAPClient.

interval => SECONDS
log => LEVEL
password => STRING
port => INTEGER
proxy => PATH
retry => NUMBER|undef
timeout => SECONDS
trace => LEVEL
username => STRING

Receiving mail

Extends "Receiving mail" in Mail::Transport::Receive.

$obj->receive( [$unique_message_id] )

Inherited, see "Receiving mail" in Mail::Transport::Receive

Server connection

Extends "Server connection" in Mail::Transport::Receive.

$obj->findBinary( $name, [@directories] )

Inherited, see "Server connection" in Mail::Transport


Inherited, see "Server connection" in Mail::Transport


Inherited, see "Server connection" in Mail::Transport


$obj->authentication( ['AUTO'|$type|$types] )

Returns a LIST of ARRAYS, each describing one possible way to contact the server. Each pair contains a mechanism name and a challenge callback (which may be undef).

The settings are used by login() to get server access. The initial value origins from new(authenticate), but may be changed later.

Available basic $types are CRAM-MD5, NTLM, and PLAIN. With AUTO, all available types will be tried. When the Authen::NTLM is not installed, the NTLM option will silently be skipped. Be warned that, because of PLAIN, erroneous username/password combinations will be passed readible as last attempt!

The NTLM authentication requires Authen::NTLM to be installed. Other methods may be added later. Besides, you may also specify a CODE reference which implements some authentication.

An ARRAY as $type can be used to specify both mechanism as callback. When no array is used, callback of the pair is set to undef. See "authenticate" in Mail::IMAPClient for the gory details.


 $transporter->authentication('CRAM-MD5', [MY_AUTH => \&c], 'PLAIN');

 foreach my $pair ($transporter->authentication)
 {   my ($mechanism, $challenge) = @$pair;
$obj->domain( [$domain] )

Used in NTLM authentication to define the Windows domain which is accessed. Initially set by new(domain) and defaults to the server's name.


Returns a boolean.

Exchanging Information

Protocol [internals]

The follow methods handle protocol internals, and should not be used by a normal user of this class.

$obj->appendMessage( $message, $foldername, [$date] )

Write the message to the server. The optional DATA can be a RFC-822 date or a timestamp.


Add a folder.

$obj->createImapClient($class, %options)

Create an object of $class, which extends Mail::IMAPClient.

All %options will be passed to the constructor (new) of $class.

$obj->currentFolder( [$foldername] )

Be sure that the specific FOLDER is the current one selected. If the folder is already selected, no IMAP traffic will be produced.

The boolean return value indicates whether the folder is selectable. It will return undef if it does not exist.


Remove one folder.


Command the server to delete for real all messages which are flagged to be deleted.

$obj->fetch(ARRAY-$of-$messages, $info)

Get some $info about the $messages from the server. The specified messages shall extend Mail::Box::Net::Message, Returned is a list of hashes, each info about one result. The contents of the hash differs per $info, but at least a message field will be present, to relate to the message in question.

The right folder should be selected before this method is called. When the connection was lost, undef is returned. Without any messages, and empty array is returned. The retrieval is done by Mail::IMAPClient method fetch(), which is then parsed.

$obj->flagsToLabels($what, @flags)
Mail::Transport::IMAP4->flagsToLabels($what, @flags)

In SCALAR context, a hash with labels is returned. In LIST context, pairs are returned.

The $what parameter can be 'SET', 'CLEAR', or 'REPLACE'. With the latter, all standard imap flags which do not appear in the list will be ignored: their value may either by set or cleared. See getFlags()

Unknown flags in @flags are stripped from their backslash and lower-cased. For instance, '\SomeWeirdFlag' will become `someweirdflag => 1'. It will be set to '1' for SET, and '0' in case of CLEAR.

example: translating IMAP4 flags into MailBox flags

 my @flags  = ('\Seen', '\Flagged');
 my $labels = Mail::Transport::IMAP4->flags2labels(SET => @flags);
$obj->folders( [$foldername] )

Returns a list of folder names which are sub-folders of the specified $foldername. Without $foldername, the top-level foldernames are returned.

$obj->getFields( $uid, $name, [$name, ...] )

Get the records with the specified NAMES from the header. The header fields are returned as list of Mail::Message::Field::Fast objects. When the name is ALL, the whole header is returned.

$obj->getFlags($folder, $id)

Returns the values of all flags which are related to the message with the specified $id. These flags are translated into the names which are standard for the MailBox suite.

A HASH is returned. Names which do not appear will also provide a value in the returned: the negative for the value is it was present.


Returns the whole text of the specified message: the head and the body.


Returns a list of UIDs which are defined by the IMAP server.


Returns the object which implements the IMAP4 protocol, an instance of a Mail::IMAPClient, which is logged-in and ready to use.

If the contact to the server was still present or could be established, an Mail::IMAPClient object is returned. Else, undef is returned and no further actions should be tried on the object.


Convert MailBox labels into IMAP flags. Returned is a string. Unsupported labels are ignored.


Returns all predefined flags as list.


Establish a new connection to the IMAP4 server, using username and password.

$obj->setFlags($id, $label, $value, [$label, $value], ...)

Change the flags on the message which are represented by the label. The value which can be related to the label will be lost, because IMAP only defines a boolean value, where MailBox labels can contain strings.

Returned is a list of $label=>$value pairs which could not be send to the IMAP server. These values may be cached in a different way.

Error handling

Extends "Error handling" in Mail::Transport::Receive.


Inherited, see "Error handling" in Mail::Reporter


Inherited, see "Error handling" in Mail::Reporter

$obj->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
Mail::Transport::IMAP4->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )

Inherited, see "Error handling" in Mail::Reporter


Inherited, see "Error handling" in Mail::Reporter

$obj->log( [$level, [$strings]] )
Mail::Transport::IMAP4->log( [$level, [$strings]] )

Inherited, see "Error handling" in Mail::Reporter


Inherited, see "Error handling" in Mail::Reporter


Inherited, see "Error handling" in Mail::Reporter


Inherited, see "Error handling" in Mail::Reporter

$obj->report( [$level] )

Inherited, see "Error handling" in Mail::Reporter

$obj->reportAll( [$level] )

Inherited, see "Error handling" in Mail::Reporter

$obj->trace( [$level] )

Inherited, see "Error handling" in Mail::Reporter


Inherited, see "Error handling" in Mail::Reporter


Extends "Cleanup" in Mail::Transport::Receive.


The connection is cleanly terminated when the program is terminated.


Error: Cannot connect to $host:$port for IMAP4: $!
Error: IMAP cannot connect to $host: $@
Notice: IMAP4 authenication $mechanism to $host:$port successful
Error: IMAP4 requires a username and password
Error: IMAP4 username $username requires a password
Error: Package $package does not implement $method.

Fatal error: the specific package (or one of its superclasses) does not implement this method where it should. This message means that some other related classes do implement this method however the class at hand does not. Probably you should investigate this and probably inform the author of the package.


This module is part of Mail-Box-IMAP4 distribution version 3.008, built on August 09, 2023. Website:


Copyrights 2001-2023 by [Mark Overmeer]. For other contributors see ChangeLog.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See