=encoding utf8

=head1 NAME

Mail::Message::Body::Nested - body of a message which contains a message

=head1 INHERITANCE

 Mail::Message::Body::Nested
   is a Mail::Message::Body
   is a Mail::Reporter

   Mail::Message::Body also extends Mail::Reporter
   is a Mail::Reporter

=head1 SYNOPSIS

  See Mail::Message::Body

  if($body->isNested) {
     my $nest = $body->nested;
     $nest->delete;
  }

=head1 DESCRIPTION

The body (content) of a message can be stored in various ways.  In this
manual-page you find the description of extra functionality you have
when a message contains a nested message, like C<message/rfc822>.

A nested message is different from a multipart message which contains
only one element, because a nested message has a full set of message
header fields defined by the RFC882, where a part of a multipart has
only a few.  But because we do not keep track whether all fields are
presented, a C<Mail::Message::Part> is used anyway.

B<WARNING:> Since 2023, at least outlook started to interpret RFC6533
incorrectly.  Bodies of type 'message/rfc822' can only be 'nested', but
when they (illegally) have Content-Transfer-Encoding, they can now behave
like normal message parts (the same as a pdf or image).

Extends L<"DESCRIPTION" in Mail::Message::Body|Mail::Message::Body/"DESCRIPTION">.

=head1 OVERLOADED

Extends L<"OVERLOADED" in Mail::Message::Body|Mail::Message::Body/"OVERLOADED">.

=over 4

=item overload: B<'""'> stringification

Inherited, see L<Mail::Message::Body/"OVERLOADED">

=item overload: B<'=='> numerical comparison

Inherited, see L<Mail::Message::Body/"OVERLOADED">

=item overload: B<'@{}'> addressed as array

Inherited, see L<Mail::Message::Body/"OVERLOADED">

=item overload: B<bool> true/false

Inherited, see L<Mail::Message::Body/"OVERLOADED">

=back

=head1 METHODS

Extends L<"METHODS" in Mail::Message::Body|Mail::Message::Body/"METHODS">.

=head2 Constructors

Extends L<"Constructors" in Mail::Message::Body|Mail::Message::Body/"Constructors">.

=over 4

=item $obj-E<gt>B<clone>()

Inherited, see L<Mail::Message::Body/"Constructors">

=item $class-E<gt>B<new>(%options)

Inherited, see L<Mail::Message::Body/"Constructors">

 -Option           --Defined in         --Default
  based_on           Mail::Message::Body  undef
  charset            Mail::Message::Body  'PERL'
  checked            Mail::Message::Body  false
  content_id         Mail::Message::Body  undef
  data               Mail::Message::Body  undef
  description        Mail::Message::Body  undef
  disposition        Mail::Message::Body  undef
  eol                Mail::Message::Body  'NATIVE'
  file               Mail::Message::Body  undef
  filename           Mail::Message::Body  undef
  language           Mail::Message::Body  undef
  message            Mail::Message::Body  undef
  mime_type          Mail::Message::Body  'message/rfc822'
  modified           Mail::Message::Body  false
  nested                                  undef
  transfer_encoding  Mail::Message::Body  'none'

=over 2

=item based_on => $body

=item charset => $charset|'PERL'|<undef>

=item checked => BOOLEAN

=item content_id => STRING

=item data => \@lines|$text

=item description => STRING|$field

=item disposition => STRING|$field

=item eol => 'CR'|'LF'|'CRLF'|'NATIVE'

=item file => $file|$handle|$io

=item filename => $file

=item language => STRING|\@lang|$field

=item message => $message

=item mime_type => STRING|$field|$mime

=item modified => BOOLEAN

=item nested => $message

The C<$message> which is encapsulated within this body.

=item transfer_encoding => STRING|$field

=back

» example: 

  my $msg   = $folder->message(3);
  my $encaps= Mail::Message::Body::Nested->new(nested => $msg);

  # The body will be coerced into a message, which lacks a few
  # lines but we do not bother.
  my $intro = Mail::Message::Body->new(data => ...);
  my $body  = Mail::Message::Body::Nested->new(nested  => $intro);

=back

=head2 Attributes

Extends L<"Attributes" in Mail::Message::Body|Mail::Message::Body/"Attributes">.

=over 4

=item $obj-E<gt>B<charsetDetectAlgorithm>( [CODE|undef|METHOD] )

Inherited, see L<Mail::Message::Body::Encode/"Attributes">

=back

=head2 Constructing a body

Extends L<"Constructing a body" in Mail::Message::Body|Mail::Message::Body/"Constructing a body">.

=over 4

=item $obj-E<gt>B<attach>(@messages, %options)

Inherited, see L<Mail::Message::Body::Construct/"Constructing a body">

=item $obj-E<gt>B<charsetDetect>(%options)

Inherited, see L<Mail::Message::Body::Encode/"Constructing a body">

=item $obj-E<gt>B<check>()

Inherited, see L<Mail::Message::Body::Encode/"Constructing a body">

=item $obj-E<gt>B<concatenate>(@components)

Inherited, see L<Mail::Message::Body::Construct/"Constructing a body">

=item $obj-E<gt>B<decoded>(%options)

Inherited, see L<Mail::Message::Body/"Constructing a body">

=item $obj-E<gt>B<encode>(%options)

Inherited, see L<Mail::Message::Body::Encode/"Constructing a body">

=item $obj-E<gt>B<encoded>(%options)

Inherited, see L<Mail::Message::Body::Encode/"Constructing a body">

=item $obj-E<gt>B<eol>( ['CR'|'LF'|'CRLF'|'NATIVE'] )

Inherited, see L<Mail::Message::Body::Encode/"Constructing a body">

=item $obj-E<gt>B<foreachLine>((CODE))

It is NOT possible to call some code for each line of a nested
because that would damage the header of the encapsulated message
Improves base, see L<Mail::Message::Body::Construct/"Constructing a body">

=item $obj-E<gt>B<stripSignature>(%options)

Inherited, see L<Mail::Message::Body::Construct/"Constructing a body">

=item $obj-E<gt>B<unify>($body)

Inherited, see L<Mail::Message::Body::Encode/"Constructing a body">

=back

=head2 The body

Extends L<"The body" in Mail::Message::Body|Mail::Message::Body/"The body">.

=over 4

=item $obj-E<gt>B<isDelayed>()

Inherited, see L<Mail::Message::Body/"The body">

=item $obj-E<gt>B<isMultipart>()

Inherited, see L<Mail::Message::Body/"The body">

=item $obj-E<gt>B<isNested>()

Inherited, see L<Mail::Message::Body/"The body">

=item $obj-E<gt>B<message>( [$message] )

Inherited, see L<Mail::Message::Body/"The body">

=item $obj-E<gt>B<partNumberOf>($part)

Inherited, see L<Mail::Message::Body/"The body">

=back

=head2 About the payload

Extends L<"About the payload" in Mail::Message::Body|Mail::Message::Body/"About the payload">.

=over 4

=item $obj-E<gt>B<charset>()

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<checked>( [BOOLEAN] )

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<contentId>( [STRING|$field] )

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<description>( [STRING|$field] )

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<disposition>( [STRING|$field] )

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<dispositionFilename>( [$directory] )

Inherited, see L<Mail::Message::Body::Encode/"About the payload">

=item $obj-E<gt>B<isBinary>()

Inherited, see L<Mail::Message::Body::Encode/"About the payload">

=item $obj-E<gt>B<isText>()

Inherited, see L<Mail::Message::Body::Encode/"About the payload">

=item $obj-E<gt>B<language>( [@langs|\@langs|$langs|$field] )

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<mimeType>()

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<nrLines>()

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<size>()

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<transferEncoding>( [STRING|$field] )

Inherited, see L<Mail::Message::Body/"About the payload">

=item $obj-E<gt>B<type>( [STRING|$field] )

Inherited, see L<Mail::Message::Body/"About the payload">

=back

=head2 Access to the payload

Extends L<"Access to the payload" in Mail::Message::Body|Mail::Message::Body/"Access to the payload">.

=over 4

=item $obj-E<gt>B<endsOnNewline>()

Inherited, see L<Mail::Message::Body/"Access to the payload">

=item $obj-E<gt>B<file>()

Inherited, see L<Mail::Message::Body/"Access to the payload">

=item $obj-E<gt>B<forNested>(CODE)

Execute the C<CODE> for the nested message.  This returns a new
nested body object.  Returns C<undef> when the C<CODE> returns C<undef>.

=item $obj-E<gt>B<lines>()

Inherited, see L<Mail::Message::Body/"Access to the payload">

=item $obj-E<gt>B<nested>()

Returns the L<Mail::Message::Part|Mail::Message::Part> message which is enclosed within
this body.

=item $obj-E<gt>B<print>( [$fh] )

Inherited, see L<Mail::Message::Body/"Access to the payload">

=item $obj-E<gt>B<printEscapedFrom>($fh)

Inherited, see L<Mail::Message::Body/"Access to the payload">

=item $obj-E<gt>B<string>()

Inherited, see L<Mail::Message::Body/"Access to the payload">

=item $obj-E<gt>B<stripTrailingNewline>()

Inherited, see L<Mail::Message::Body/"Access to the payload">

=item $obj-E<gt>B<write>(%options)

Inherited, see L<Mail::Message::Body/"Access to the payload">

=back

=head2 Internals

Extends L<"Internals" in Mail::Message::Body|Mail::Message::Body/"Internals">.

=over 4

=item $any-E<gt>B<addTransferEncHandler>( $name, <$class|$object> )

Inherited, see L<Mail::Message::Body::Encode/"Internals">

=item $obj-E<gt>B<contentInfoFrom>($head)

Inherited, see L<Mail::Message::Body/"Internals">

=item $obj-E<gt>B<contentInfoTo>($head)

Inherited, see L<Mail::Message::Body/"Internals">

=item $obj-E<gt>B<fileLocation>( [$begin, $end] )

Inherited, see L<Mail::Message::Body/"Internals">

=item $obj-E<gt>B<getTransferEncHandler>($type)

Inherited, see L<Mail::Message::Body::Encode/"Internals">

=item $obj-E<gt>B<isModified>()

Inherited, see L<Mail::Message::Body/"Internals">

=item $obj-E<gt>B<load>()

Inherited, see L<Mail::Message::Body/"Internals">

=item $obj-E<gt>B<modified>( [BOOLEAN] )

Inherited, see L<Mail::Message::Body/"Internals">

=item $obj-E<gt>B<moveLocation>( [$distance] )

Inherited, see L<Mail::Message::Body/"Internals">

=item $obj-E<gt>B<read>( $parser, $head, $bodytype, [$chars, [$lines]] )

Inherited, see L<Mail::Message::Body/"Internals">

=back

=head2 Error handling

Extends L<"Error handling" in Mail::Message::Body|Mail::Message::Body/"Error handling">.

=over 4

=item $obj-E<gt>B<AUTOLOAD>()

Inherited, see L<Mail::Message::Body/"Error handling">

=item $obj-E<gt>B<notImplemented>()

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<notImplemented>()

Inherited, see L<Mail::Reporter/"Error handling">

=back

=head2 Cleanup

Extends L<"Cleanup" in Mail::Message::Body|Mail::Message::Body/"Cleanup">.

=over 4

=item $obj-E<gt>B<DESTROY>()

Inherited, see L<Mail::Reporter/"Cleanup">

=item $obj-E<gt>B<DESTROY>()

Inherited, see L<Mail::Reporter/"Cleanup">

=back

=head1 DETAILS

Extends L<"DETAILS" in Mail::Message::Body|Mail::Message::Body/"DETAILS">.

=head1 DIAGNOSTICS

=over 4

=item Warning: Content-Transfer-Encoding '$te' requires explicit charset, defaulted to utf-8.

Cast by C<encode()>

=item Error: cannot concatenate element $which

Cast by C<concatenate()>

=item Fault: cannot open $file to write body: $!

Cast by C<write()>

=item Warning: charset '$name' is not known.

The encoding or decoding of a message body encounters a character set which
is not understood by Perl's Encode module.
Cast by C<encode()>

=item Error: class $package does not implement method $method.

Fatal error: the specific C<$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 C<notImplemented()>

=item Error: class $package does not implement method $method.

Fatal error: the specific C<$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 C<notImplemented()>

=item Error: data not convertible to a message (type is $class)

Cast by C<new()>

=item Fault: error closing $file after write body: $!

Cast by C<write()>

=item Warning: no decoder defined for transfer encoding '$encoding'.

The data (message body) is encoded in a way which is not currently understood,
therefore no decoding (or recoding) can take place.
Cast by C<encode()>

=item Warning: no encoder defined for transfer encoding '$encoding'.

The data (message body) has been decoded, but the required encoding is
unknown.  The decoded data is returned.
Cast by C<encode()>

=item Error: no filename parameter for write() body.

Cast by C<write()>

=item Error: part number needs multi-part or nested.

Cast by C<partNumberOf()>

=item Error: unknown line terminator '$eol'.

Cast by C<eol()>

=item Error: you cannot use foreachLine on a nested.

L<foreachLine()|Mail::Message::Body::Nested/"METHODS"> should be used on decoded message bodies only, because
it would modify the header of the encapsulated message. which is
clearly not acceptable.
Cast by C<foreachLine()>

=back

=head1 SEE ALSO

This module is part of Mail-Message version 4.05,
built on April 10, 2026. Website: F<http://perl.overmeer.net/mailbox/>

=head1 LICENSE

For contributors see file ChangeLog.

This software is copyright (c) 2001-2026 by Mark Overmeer.

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

