Mail::Box::POP3 - handle POP3 folders as client


   is a Mail::Box::Net
   is a Mail::Box
   is a Mail::Reporter


 use Mail::Box::POP3;
 my $folder = new Mail::Box::POP3 folder => $ENV{MAIL}, ...;


Maintain a folder which has its messages stored on a remote server. The communication between the client application and the server is implemented using the POP3 protocol. This class uses Mail::Transport::POP3 to hide the transport of information, and focusses solely on the correct handling of messages within a POP3 folder.


overload: ""

overload: @{}

overload: cmp




    For authentications, you have three choices: specify a foldername which resembles an URL, or specify a pop-client object, or separate options for user, password, pop-server and server-port.

     Option           --Defined in     --Default
     access             Mail::Box        'r'
     authenticate                        'AUTO'
     body_delayed_type  Mail::Box        Mail::Message::Body::Delayed
     body_type          Mail::Box        Mail::Message::Body::Lines
     coerce_options     Mail::Box        []
     create             Mail::Box        <not applicable>
     extract            Mail::Box        10240
     field_type         Mail::Box        undef
     fix_headers        Mail::Box        <false>
     folder             Mail::Box        <not applicable>
     folderdir          Mail::Box        <not used>
     head_delayed_type  Mail::Box        Mail::Message::Head::Delayed
     head_type          Mail::Box        Mail::Message::Head::Complete
     keep_dups          Mail::Box        <false>
     lock_file          Mail::Box        undef
     lock_timeout       Mail::Box        1 hour
     lock_type          Mail::Box        'NONE'
     lock_wait          Mail::Box        10 seconds
     locker             Mail::Box        undef
     log                Mail::Reporter   'WARNINGS'
     manager            Mail::Box        undef
     message_type       Mail::Box        Mail::Box::POP3::Message
     multipart_type     Mail::Box        Mail::Message::Body::Multipart
     password           Mail::Box::Net   undef
     pop_client                          undef
     remove_when_empty  Mail::Box        <false>
     save_on_exit       Mail::Box        <true>
     server_name        Mail::Box::Net   undef
     server_port        Mail::Box::Net   110
     trace              Mail::Reporter   'WARNINGS'
     trusted            Mail::Box        <false>
     username           Mail::Box::Net   undef

    . access => MODE

    . authenticate => 'LOGIN'|'APOP'|'AUTO'

      POP3 can use two methods of authentication: the old LOGIN protocol, which transmits a username and password in plain text, and the newer APOP protocol which uses MD5 encryption. APOP is therefore much better, however not always supported by the server. With AUTO, first APOP is tried and if that fails LOGIN.

    . body_delayed_type => CLASS

    . body_type => CLASS|CODE

    . coerce_options => ARRAY

    . create => BOOLEAN

    . extract => INTEGER | CODE | METHOD | 'LAZY'|'ALWAYS'

    . field_type => CLASS

    . fix_headers => BOOLEAN

    . folder => FOLDERNAME

    . folderdir => DIRECTORY

    . head_delayed_type => CLASS

    . head_type => CLASS

    . keep_dups => BOOLEAN

    . lock_file => FILENAME

    . lock_timeout => SECONDS

    . lock_type => CLASS|STRING|ARRAY

    . lock_wait => SECONDS

    . locker => OBJECT

    . log => LEVEL

    . manager => MANAGER

    . message_type => CLASS

    . multipart_type => CLASS

    . password => STRING

    . pop_client => OBJECT

      You may want to specify your own pop-client object. The object which is passed must extend Mail::Transport::POP3.

    . remove_when_empty => BOOLEAN

    . save_on_exit => BOOLEAN

    . server_name => HOSTNAME

    . server_port => INTEGER

    . trace => LEVEL

    . trusted => BOOLEAN

    . username => STRING


     my $url = 'pop3://'
     my $pop = Mail::Box::POP3->new($url);
     my $pop = $mgr->open(type => 'pop3',
        username => 'myname', password => 'mypassword',
        server_name => '');

The folder


    It is impossible to write messages to the average POP3 server. There are extensions to the protocol which do permit it, however these are not implemented (yet, patches welcome).

    undef is returned, and an error displayed. However, no complaint is given when the MESSAGE is undef itself.

     Option--Defined in--Default
     share   Mail::Box   <not used>

    . share => BOOLEAN


    As useless as addMessage(). The only acceptable call to this method is without any message.



$obj->copyTo(FOLDER, OPTIONS)


    It is not possible to delete a POP3 folder remotely: the best we can do is remove all the messages in it... which is the action implemented here. A notice is logged about this.

     Option   --Defined in--Default
     recursive  Mail::Box   <not used>

    . recursive => BOOLEAN









Folder flags





The messages



$obj->findFirstLabeled(LABEL, [BOOLEAN, [ARRAY-OF-MSGS]])

$obj->message(INDEX [,MESSAGE])

$obj->messageId(MESSAGE-ID [,MESSAGE])








    The standard POP3 protocol does not support sub-folders, so an empty list will be returned in any case.

     Option    --Defined in     --Default
     check       Mail::Box        <false>
     folder      Mail::Box        <from calling object>
     folderdir   Mail::Box        <from folder>
     skip_empty  Mail::Box        <false>

    . check => BOOLEAN

    . folder => FOLDERNAME

    . folderdir => DIRECTORY

    . skip_empty => BOOL

$obj->nameOfSubFolder(SUBNAME, [PARENTNAME])

Mail::Box::POP3->nameOfSubFolder(SUBNAME, [PARENTNAME])



    It is not possible to open a sub-folder for a POP3 folder, because that is not supported by the official POP3 protocol. In any case, undef is returned to indicate a failure.




$obj->coerce(MESSAGE, OPTIONS)

$obj->create(FOLDER, OPTIONS)

Mail::Box::POP3->create(FOLDER, OPTIONS)

    It is not possible to create a new folder on a POP3 server. This method will always return false.

     Option   --Defined in--Default
     folderdir  Mail::Box   <not used>

    . folderdir => DIRECTORY

$obj->determineBodyType(MESSAGE, HEAD)

Mail::Box::POP3->foundIn([FOLDERNAME], OPTIONS)


    Read the header for the specified message from the remote server.


    Read all data for the specified message from the remote server.




    Returns the pop client object. This does not establish the connection.









     Option  --Defined in--Default
     messages  Mail::Box   <required>

    . messages => ARRAY

Other methods



Error handling






$obj->log([LEVEL [,STRINGS]])

Mail::Box::POP3->log([LEVEL [,STRINGS]])













How POP3 folders work

Rfc1939 defines how POP3 works. POP3 is a really simple protocol to receive messages from a server to a user's client. POP3 is also really limited: it can only be used to fetch messages, but has not many ways to limit the amount of network traffic, like the IMAP4 protocol has.

One POP3 account represents only one folder: there is no way of sub-folders in POP3. POP3 doesn't support writing (except for some message status flags).

This implementation

The protocol specifics are implemented in Mail::Transport::POP3, written by Liz Mattijsen. That module does not use any of the other POP3 modules available on CPAN for the reason that MailBox tries to be smarter: it is capable of re-establishing broken POP3 connection when the server supports UIDs.

The implementation has shown to work with many different POP servers. In the test directory of the distribution, you will find a small server implementation, which is used to test the client.


Error: Cannot create POP3 client for $name.

    The connection to the POP3 server cannot be established. You may see more, related, error messages about the failure.

Error: Cannot find head back for $uidl on POP3 server $name.

    The server told to have this message, but when asked for its headers, no single line was returned. Did the message get destroyed?

Error: Cannot read body for $uidl on POP3 server $name.

    The message's headers are retreived from the server, but the body seems to be lost. Did the message get destroyed between reading the header and reading the body?

Warning: Changes not written to read-only folder $self.

    You have opened the folder read-only --which is the default set by new(access)--, made modifications, and now want to close it. Set close(force) if you want to overrule the access mode, or close the folder with close(write) set to NEVER.

Error: Copying failed for one message.

    For some reason, for instance disc full, removed by external process, or read-protection, it is impossible to copy one of the messages. Copying will proceed for the other messages.

Error: Destination folder $name is not writable.

    The folder where the messages are copied to is not opened with write access (see new(access)). This has no relation with write permission to the folder which is controled by your operating system.

Warning: Different messages with id $msgid

    The message id is discovered more than once within the same folder, but the content of the message seems to be different. This should not be possible: each message must be unique.

Error: Folder $name is opened read-only

    You can not write to this folder unless you have opened the folder to write or append with new(access), or the force option is set true.

Error: Invalid timespan '$timespan' specified.

    The string does not follow the strict rules of the time span syntax which is permitted as parameter.

Warning: Message $uidl on POP3 server $name disappeared.

    The server indicated the existence of this message before, however it has no information about the message anymore.

Warning: Message-id '$msgid' does not contain a domain.

    According to the RFCs, message-ids need to contain a unique random part, then an @, and then a domain name. This is made to avoid the creation of two messages with the same id. The warning emerges when the @ is missing from the string.

Warning: POP3 folders cannot be deleted.

    Each user has only one POP3 folder on a server. This folder is created and deleted by the server's administrator only.

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.

Error: Unable to create subfolder $name of $folder.

    The copy includes the subfolders, but for some reason it was not possible to copy one of these. Copying will proceed for all other sub-folders.

Error: Update of $nr messages ignored for POP3 folder $name.

    The standard POP3 implementation does not support writing from client back to the server. Therefore, modifications may be lost.

Error: Writing folder $name failed

    For some reason (you probably got more error messages about this problem) it is impossible to write the folder, although you should because there were changes made.

Error: You cannot write a message to a pop server (yet)

    Some extensions to the POP3 protocol do permit writing messages to the server, but the standard protocol only implements retreival. Feel invited to extend our implementation with writing.


This module is part of Mail-Box distribution version 2.084, built on September 26, 2008. Website:


Copyrights 2001-2008 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