Mail::Box::MH(3pm)

📦

version 4.02 · 9 versions

✨ NAME ✨

Mail::Box::MH - handle MH folders 💅✨

okay bestie, this is the Mail::Box::MH(3pm) page, and it's literally all about handling MH folders. The object is Mail::Box::MH, and it's giving folder-management main character energy. No cap.

🌸 INHERITANCE 🌸

The way this class is built is a whole lineage, and it's iconic:

Mail::Box::MH
  is a Mail::Box::Dir
  is a Mail::Box
  is a Mail::Reporter

so Mail::Box::MH is a Mail::Box::Dir, which is a Mail::Box, which is a Mail::Reporter. periodt.

🦋 SYNOPSIS 🦋

Bestie, here's the starter code:

use Mail::Box::MH;
my $folder = Mail::Box::MH->new(folder => $ENV{MAIL}, ...);

Load the module, then create a new folder object with folder => $ENV{MAIL}, and that ... means there's more stuff you can pass. Iykyk.

💖 DESCRIPTION 💖

bestie, this doc is here to explain how MH mailboxes work and what you can do with the MH folder object Mail::Box::MH. That's the whole vibe: MH mailboxes + the Mail::Box::MH object. Obsessed.

Extends "DESCRIPTION" in Mail::Box::Dir.

👑 OVERLOADED 👑

Extends "OVERLOADED" in Mail::Box::Dir.

overload: '""' stringification 🎀

Inherited, see "OVERLOADED" in Mail::Box 💖

overload: '@{}' use as ARRAY 🦋

Inherited, see "OVERLOADED" in Mail::Box 💖

overload: cmp string comparison ⭐

Inherited, see "OVERLOADED" in Mail::Box 💖

# ✨ METHODS ✨

Extends "METHODS" in Mail::Box::Dir. So like, everything cool here? It's building on the dir-level stuff, bestie 🫶

🎀 Constructors 🎀

Extends "Constructors" in Mail::Box::Dir.

`$class->new(%options)`

Inherited, go read "Constructors" in Mail::Box 💖

Here's the full default lineup, no cap — every single one:

-Option           --Defined in     --Default
 access             Mail::Box        'r'
 body_delayed_type  Mail::Box        Mail::Message::Body::Delayed
 body_type          Mail::Box        Mail::Message::Body::Lines
 coerce_options     Mail::Box        +[]
 create             Mail::Box        false
 directory          Mail::Box::Dir   <derived from folder name>
 extract            Mail::Box        10240
 field_type         Mail::Box        undef
 fix_headers        Mail::Box        false
 folder             Mail::Box        $ENV{MAIL}
 folderdir          Mail::Box        $ENV{HOME}/.mh
 head_delayed_type  Mail::Box        Mail::Message::Head::Delayed
 head_type          Mail::Box        Mail::Message::Head::Complete
 index                               undef
 index_filename                      <foldername>/.index
 index_type                          Mail::Box::MH::Index
 keep_dups          Mail::Box        false
 keep_index                          false
 labels                              undef
 labels_filename                     <foldername>/.mh_sequence
 labels_type                         Mail::Box::MH::Labels
 lock_file          Mail::Box        <index_file>
 lock_timeout       Mail::Box        1 hour
 lock_type          Mail::Box        Mail::Box::Locker::DotLock
 lock_wait          Mail::Box        10 seconds
 locker             Mail::Box        undef
 manager            Mail::Box        undef
 message_type       Mail::Box        <folder-class>::Message
 multipart_type     Mail::Box        Mail::Message::Body::Multipart
 remove_when_empty  Mail::Box        true
 save_on_exit       Mail::Box        true
 trusted            Mail::Box        <depends on folder location>

Okay now the one-by-one moment 💅

access => $mode — defined over in Mail::Box.
body_delayed_type => CLASS — defined over in Mail::Box.
body_type => CLASS|CODE — defined over in Mail::Box.
coerce_options => ARRAY — defined over in Mail::Box.
create => BOOLEAN — defined over in Mail::Box.
directory => $directory — defined over in Mail::Box::Dir.
extract => INTEGER|CODE|METHOD|'LAZY'|'ALWAYS' — defined over in Mail::Box.
field_type => $class — defined over in Mail::Box.
fix_headers => BOOLEAN — defined over in Mail::Box.
folder => $name — defined over in Mail::Box.
folderdir => $directory — defined over in Mail::Box.
head_delayed_type => $class — defined over in Mail::Box.
head_type => $class — defined over in Mail::Box.
index => $object — you can hand in an $object of a type that extends Mail::Box::MH::Index (at the absolute bare minimum it's gotta implement a get() method), and it works as an alternative for the index file reader that "Mail::Box::MH" would otherwise create ✨
index_filename => $file — this is the $file used in each directory to store the headers of all the mails. Heads up bestie: the filename must not contain a directory path. Like, do not use "/usr/people/jan/.index", and do not use "subdir/.index" — just say ".index" 🎀
index_type => $class — defined over in Mail::Box.
keep_dups => BOOLEAN — defined over in Mail::Box.
keep_index => BOOLEAN — keeps an index file for the specified mailbox, one file per directory. Using an index file speeds things up considerably, because it avoids reading every single message file the moment you open the folder. When you open a folder, you can use the index file to grab info like the subject of each message, instead of having to read possibly thousands of messages 😭 iconic behaviour honestly
labels => $object — you can specify an $object of a type that extends Mail::Box::MH::Labels (minimum requirement: it implements the get() method), as an alternative for the labels file reader as created by "Mail::Box::MH" 🦋
labels_filename => $file — in MH-folders, messages can be labeled, for instance based on the sender or whether it's read or not. That status is kept in a $file which is usually called ".mh_sequences", but that name can be overruled with this flag ✨
labels_type => $class — defined over in Mail::Box.
lock_file => $file — defined over in Mail::Box.
lock_timeout => $seconds — defined over in Mail::Box.
lock_type => $class|$name|\@names — defined over in Mail::Box.
lock_wait => $seconds — defined over in Mail::Box.
locker => $locker — defined over in Mail::Box.
manager => $manager — defined over in Mail::Box.
message_type => $class — defined over in Mail::Box.
multipart_type => CLASS — defined over in Mail::Box.
remove_when_empty => BOOLEAN — defined over in Mail::Box.
save_on_exit => BOOLEAN — defined over in Mail::Box.
trusted => BOOLEAN — defined over in Mail::Box.

🌸 Attributes 🌸

Extends "Attributes" in Mail::Box::Dir.

$obj->fixHeaders() — inherited, see "Attributes" in Mail::Box
$obj->folderdir( [$directory] ) — inherited, see "Attributes" in Mail::Box
$obj->isTrusted() — inherited, see "Attributes" in Mail::Box
$obj->name() — inherited, see "Attributes" in Mail::Box
$obj->removeEmpty() — inherited, see "Attributes" in Mail::Box
$obj->type() — inherited, see "Attributes" in Mail::Box

🦋 The folder 🦋

Extends "The folder" in Mail::Box::Dir.

$obj->addMessage($message, %options) — inherited, see "The folder" in Mail::Box
$obj->addMessages(@messages) — inherited, see "The folder" in Mail::Box

`$class->appendMessages(%options)`

Appends a message to a folder that isn't open. Improves on the base — see "The folder" in Mail::Box 🔥

-Option  --Defined in     --Default
 folder    Mail::Box        <required>
 message   Mail::Box        undef
 messages  Mail::Box        undef
 share     Mail::Box        false

folder => $name — defined over in Mail::Box.
message => $message — defined over in Mail::Box.
messages => $message|\@messages — defined over in Mail::Box.
share => BOOLEAN — defined over in Mail::Box.
$obj->close(%options) — inherited, see "The folder" in Mail::Box
$obj->copyTo($folder, %options) — inherited, see "The folder" in Mail::Box
$obj->delete(%options) — inherited, see "The folder" in Mail::Box
$obj->directory() — inherited, see "The folder" in Mail::Box::Dir
$obj->organization() — inherited, see "The folder" in Mail::Box
$obj->size() — inherited, see "The folder" in Mail::Box
$obj->update(%options) — inherited, see "The folder" in Mail::Box
$obj->url() — inherited, see "The folder" in Mail::Box

🎀 Folder flags 🎀

Extends "Folder flags" in Mail::Box::Dir.

$obj->access() — inherited, see "Folder flags" in Mail::Box
$obj->isModified() — inherited, see "Folder flags" in Mail::Box
$obj->modified( [BOOLEAN] ) — inherited, see "Folder flags" in Mail::Box
$obj->writable() — inherited, see "Folder flags" in Mail::Box

💌 The messages 💌

Extends "The messages" in Mail::Box::Dir.

$obj->current( [$number|$message|$message_id] ) — inherited, see "The messages" in Mail::Box
$obj->find($message_id) — inherited, see "The messages" in Mail::Box
$obj->findFirstLabeled( $label, [BOOLEAN, [\@msgs]] ) — inherited, see "The messages" in Mail::Box
$obj->message( $index, [$message] ) — inherited, see "The messages" in Mail::Box
$obj->messageId( $message_id, [$message] ) — inherited, see "The messages" in Mail::Box
$obj->messageIds() — inherited, see "The messages" in Mail::Box
$obj->messages( <'ALL'|$range|'ACTIVE'|'DELETED'|$label| !$label|$filter> ) — inherited, see "The messages" in Mail::Box
$obj->nrMessages(%options) — inherited, see "The messages" in Mail::Box
$obj->scanForMessages($message, $message_ids, $timespan, $window) — inherited, see "The messages" in Mail::Box

🌈 Sub-folders 🌈

Extends "Sub-folders" in Mail::Box::Dir.

$any->listSubFolders(%options) — inherited, see "Sub-folders" in Mail::Box
$any->nameOfSubFolder( $subname, [$parentname] ) — inherited, see "Sub-folders" in Mail::Box
$obj->openRelatedFolder(%options) — inherited, see "Sub-folders" in Mail::Box
$obj->openSubFolder() — inherited, see "Sub-folders" in Mail::Box
$any->topFolderWithMessages() — inherited, see "Sub-folders" in Mail::Box

🔧 Internals 🔧

Extends "Internals" in Mail::Box::Dir.

$obj->coerce($message, %options) — inherited, see "Internals" in Mail::Box

`$any->create($foldername, %options)`

Inherited, see "Internals" in Mail::Box

-Option   --Defined in--Default
 folderdir  Mail::Box   undef

folderdir => $directory — defined over in Mail::Box.
$obj->determineBodyType($message, $head) — inherited, see "Internals" in Mail::Box
$obj->folderToDirectory($foldername, $folderdir) — inherited, see "Internals" in Mail::Box::Dir
$class->foundIn( [$foldername], %options ) — inherited, see "Internals" in Mail::Box
$obj->highestMessageNumber() — returns the highest number that's used in the folder to store a file. You can call this when the folder is read (and then the number can be derived with zero file-system access), but also when the folder isn't read yet 👑
$obj->index() — creates an index reader/writer object ✨
$obj->labels() — creates a label reader/writer object 🎀
$obj->lineSeparator( [<STRING|'CR'|'LF'|'CRLF'>] ) — inherited, see "Internals" in Mail::Box
$obj->locker() — inherited, see "Internals" in Mail::Box
$obj->messageInFile($filename) — inherited, see "Internals" in Mail::Box::Dir
$obj->read(%options) — inherited, see "Internals" in Mail::Box
$obj->readMessageFilenames($directory) — inherited, see "Internals" in Mail::Box::Dir
$obj->readMessages(%options) — inherited, see "Internals" in Mail::Box
$obj->storeMessage($message) — inherited, see "Internals" in Mail::Box
$obj->toBeThreaded($messages) — inherited, see "Internals" in Mail::Box
$obj->toBeUnthreaded($messages) — inherited, see "Internals" in Mail::Box
$obj->updateMessages(%options) — inherited, see "Internals" in Mail::Box
$obj->write(%options) — inherited, see "Internals" in Mail::Box

`$obj->writeMessages(%options)`

Inherited, see "Internals" in Mail::Box

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

messages => ARRAY — defined over in Mail::Box.
renumber => BOOLEAN — permits renumbering of messages. By default this is "true", but for some unknown reason, you may be thinking that messages should not be renumbered 🙈

⭐ Other methods ⭐

Extends "Other methods" in Mail::Box::Dir.

$any->timespan2seconds($time) — inherited, see "Other methods" in Mail::Box

💀 Error handling 💀

Extends "Error handling" in Mail::Box::Dir.

$obj->AUTOLOAD() — inherited, see "Error handling" in Mail::Reporter
$obj->notImplemented() — inherited, see "Error handling" in Mail::Reporter

🧚 Cleanup 🧚

Extends "Cleanup" in Mail::Box::Dir.

$obj->DESTROY() — inherited, see "Cleanup" in Mail::Box

💫 DETAILS 💫

Extends "DETAILS" in Mail::Box::Dir.

🌸 Different kinds of folders

Extends "Different kinds of folders" in Mail::Box::Dir.

🌸 Available folder types

Extends "Available folder types" in Mail::Box::Dir.

🌸 Folder class implementation

Extends "Folder class implementation" in Mail::Box::Dir.

🌸 How MH folders work

okay so MH-type folders use a directory to store the messages of one folder. Every message gets its very own separate file, main character energy, no sharing. And lowkey that's a slay, because changes in a folder only touch a few of these small files — unlike file-based folders, where one lil change in the folder forces a rewrite of the huge folder files. 🫶

but bestie… plot twist 😭 MH-based folders perform very bad if you need header information of all messages. Say you want full knowledge about all message-threads (see Mail::Box::Thread::Manager) in the folder — that requires reading all the header lines in all the message files. And usually, reading your messages in threads is desired. so yeah. it's giving consequences.

So, each message is written in a separate file. The filenames are numbers, which count from 1. Next to these message files, a directory may contain a file named .mh_sequences, storing labels which relate to the messages. Furthermore, a folder-directory may contain sub-directories, which are seen as sub-folders. ✨

🌸 This implementation

This implementation supports the .mh-sequences file and sub-folders. 💅 Next to this, considerable effort it made to avoid reading each message-file. This should boost performance of the MailBox distribution over other Perl-modules which are able to read folders.

Folder types which store their messages each in one file, together in one directory, are bad for performance. Consider that you want to know the subjects of all messages, while browser through a folder with your mail-reading client. This would cause all message-files to be read.

Mail::Box::MH has two ways to try improve performance. You can use an index-file, and use on delay-loading. The combination performs even better. Both are explained in the next sections. 👑

🌸 An index-file

If you specify new(keep_index), then all header-lines of all messages from the folder which have been read once, will also be written into one dedicated index-file (one file per folder). The default filename is .index. 🎀

However, index-files are not supported by any other reader which supports MH (as far as I know). If you read the folders with such I client, it will not cause unrecoverable conflicts with this index-file, but at most be bad for performance.

If you do not (want to) use an index-file, then delay-loading may save your day. 🌈

💀 DIAGNOSTICS 💀

okay bestie, vibe check time — these are the messages this module can throw at you, and what each one actually means. ngl they're kinda dramatic but they're all facts.

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". Cast by write()
Error: cannot append message without lock on $folder. — It is impossible to append one or more messages to the folder which is not opened, because locking it fails. The folder may be in use by an other application, or you may need to specify some lock related options (see new()). Cast by appendMessages()
Fault: cannot create MH folder $name: $! — For some reason, it is impossible to create the folder. Check the permissions and the $name of the folder. Does the path to the directory to be created exist? Cast by create()
Fault: cannot create directory $dir for subfolder $name: $! — Cast by openSubFolder()
Error: cannot write folder $name without lock. — It is impossible to get a lock on the folder, which means that the changes can not be made. You may need to tune the lock related options which are available at folder creation. Cast by writeMessages()
Warning: changes not written to read-only folder $name. — 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". Cast by close()
Error: class $package does not implement method $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. Cast by notImplemented()
Error: copying failed for one message. — For some reason, for instance disk full, removed by external process, or read-protection, it is impossible to copy one of the messages. Copying will proceed for the other messages. Cast by copyTo()
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 controlled by your operating system. Cast by copyTo()
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. Cast by messageId()
Warning: folder $name not deleted: not writable. — The folder must be opened with write access via new(access), otherwise removing it will be refused. So, you may have write-access according to the operating system, but that will not automatically mean that this "delete" method permits you to. The reverse remark is valid as well. Cast by delete()
Error: invalid timespan '$span'. — The string does not follow the strict rules of the time span syntax which is permitted as parameter. Cast by timespan2seconds()
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. Cast by messageId()
Error: unknown value to folder->close(write => $when). — Cast by close()
Error: you cannot add a message which is already part of a folder to a new one. Please use moveTo or copyTo. — Cast by addMessage()

🦋 SEE ALSO 🦋

This module is part of Mail-Box version 4.02, built on April 10, 2026.

Website: http://perl.overmeer.net/CPAN/

👑 LICENSE 👑

For contributors see file ChangeLog.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

and that's the whole page, bestie!! 🎀 this one is Mail::Box::MH(3pm) from perl v5.40.1, dated 2026-05-09 — go forth and read your mail folders, you absolute icon 💅✨

📦 where this page comes from

ubuntu stonking: libmail-box-perl 4.02-1 · Artistic-1.0-Perl OR GPL-1.0-or-later
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-03: a language model's rewrite of the original, under its terms