NAME

Email::MIME::CreateHTML - Multipart HTML Email builder

SYNOPSIS

        use Email::MIME::CreateHTML;
        my $email = Email::MIME->create_html(
                header => [
                        From => 'my@address',
                        To => 'your@address',
                        Subject => 'Here is the information you requested',
                ],
                body => $html,
                text_body => $plain_text
        );

        use Email::Send;
        my $sender = Email::Send->new({mailer => 'SMTP'});
        $sender->mailer_args([Host => 'smtp.example.com']);
        $sender->send($email);

DESCRIPTION

This module allows you to build HTML emails, optionally with a text-only alternative and embedded media objects. For example, an HTML email with an alternative version in plain text and with all the required images contained in the mail.

The HTML content is parsed looking for embeddable media objects. A resource loading routine is used to fetch content from those URIs and replace the URIs in the HTML with CIDs. The default resource loading routine is deliberately conservative, only allowing resources to be fetched from the local filesystem. It's possible and relatively straightforward to plug in a custom resource loading routine that can resolve URIs using a broader range of protocols. An example of one using LWP is given later in the "COOKBOOK".

The MIME structure is then assembled, embedding the content of the resources where appropriate. Note that this module does not send any mail, it merely does the work of building the appropriate MIME message. The message can be sent with Email::Send or any other mailer that can be fed a string representation of an email message.

Mail Construction

The mail construction is compliant with rfc2557.

HTML, no embedded objects (images, flash, etc), no text alternative

  text/html

HTML, no embedded objects, with text alternative

  multipart/alternative
          text/plain
          text/html

HTML with embedded objects, no text alternative

  multipart/related
          text/html
          embedded object one
          embedded object two
          ...

HTML with embedded objects, with text alternative

  multipart/alternative
          text/plain
          multipart/related
                  text/html
                  embedded object one
                  embedded object two
                  ...

METHODS

There is only one method, which is installed into the Email::MIME package:

Email::MIME->create_html(%parameters): This method creates an Email::MIME object from a set of named parameters. Of these the "header" and "body" parameters are mandatory and all others are optional. See the "PARAMETERS" section for more information.

LOW-LEVEL API

Email::MIME::CreateHTML also defines a lower-level interface of 3 building-block routines that you can use for finer-grain construction of HTML mails. These may be optionally imported:

        use Email::MIME::CreateHTML qw(embed_objects parts_for_objects build_html_mail);

($modified_html, $cid_mapping) = embed_objects($html, \%options)

This parses the HTML and replaces URIs in the embed list with a CID. The modified HTML and CID to URI mapping is returned. Relevant parameters are:

        embed
        inline_css
        base
        object_cache
        resolver

The meanings and defaults of these parameters are explained below.

@mime_parts = parts_for_objects($cid_mapping, \%options)

This creates a list of Email::MIME parts for each of the objects in the supplied CID mapping. Relevant options are:

        base
        object_cache
        resolver

The meanings and defaults of these parameters are explained below.

$email = build_html_email(\@headers, $html, \%body_attributes, \@html_mime_parts, $plain_text_mime)

The assembles a ready-to-send Email::MIME object (that can be sent with Email::Send).

PARAMETERS

header => list

A list reference containing a set of headers to be created. If no Date header is specified, one will be provided for you based on the gmtime() of the local machine.

body => scalar

A scalar value holding the HTML message body.

body_attributes => hash reference

This is passed as the attributes parameter to the "create" method (supplied by "Email::MIME::Creator") that creates the html part of the mail. The body content-type will be set to "text/html" unless it is overidden here.

embed => boolean

Attach relative images and other media to the message. This is enabled by default. The module will attempt to embed objects defined by "embed_elements". Note that this option only affects the parsing of the HTML and will not affect the "objects" option.

The object's URI will be rewritten as a Content ID.

embed_elements => reference to hash of hashes with boolean values

The set of elements that you want to be embedded. Defaults to the %Email::MIME::CreateHTML::EMBED package global. This should be a data structure of the form:

        embed_elements => {
                $elementname_1 => {$attrname_1 => $boolean_1},
                $elementname_2 => {$attrname_2 => $boolean_2},
                ...
        }

i.e. resource will be embedded if "$embed_elements->{$elementname}->{$attrname}" is true.

resolver => object

If a resolver is supplied this will be used to fetch the resources that are embedded as MIME objects in the email. If no resolver is given the default behaviour is to choose the best available resolver to read $uri with any $base value prefixed. Resources fetched using the resolver will be cached if an "object_cache" is supplied.

base => scalar

This must be a filepath or a URI.

If "embed" is true (the default) then "base" will be used when fetching the objects.

Examples of good bases:

  ./local/images
  /home/somewhere/images
  http://mywebserver/images

inline_css => boolean

Inline any CSS external CSS files referenced through link elements. Enabled by default. Some mail clients will only interpret css if it is inlined.

objects => hash reference

A reference to a hash of external objects. Keys are Content Ids and the values are filepaths or URIs used to fetch the resource with the resolver. We use "MIME::Types" to derive the type from the file extension. For example in an HTML mail you would use the file keyed on '12345678@bbc.co.uk' like "<img src="cid:12345678@bbc.co.uk" alt="a test" width="20" height="20" />"

object_cache => cache object

A cache object can be supplied to cache external resources such as images. This must support the following interface:

        $o = new ...
        $o->set($key, $value)
        $value = $o->get($key)

Both the Cache and Cache::Cache distributions on CPAN conform to this.

text_body => scalar

A scalar value holding the contents of an additional plain text message body.

text_body_attributes => hash reference

This is passed as the attributes parameter to the "create" method (supplied by "Email::MIME::Creator") that creates the plain text part of the mail. The body Content-Type will be set to "text/plain" unless it is overidden here.

GLOBAL VARIABLES

%Email::MIME::CreateHTML::EMBED

This is the default set of elements (and the relevant attributes that point at a resource) that will be embedded. The for this is:

        'bgsound' => {'src'=>1},
        'body'    => {'background'=>1},
        'img'     => {'src'=>1},
        'input'   => {'src'=>1},
        'table'   => {'background'=>1},
        'td'      => {'background'=>1},
        'th'      => {'background'=>1},
        'tr'      => {'background'=>1}

You can override this using the "embed_elements" parameter.

COOKBOOK

The basics

This builds an HTML email:

        my $email = Email::MIME->create_html(
                header => [
                        From => 'my@address',
                        To => 'your@address',
                        Subject => 'My speedy HTML',
                ],
                body => $html
        );

If you want a plaintext alternative, include the "text_body" option:

        my $email = Email::MIME->create_html(
                header => [
                        From => 'my@address',
                        To => 'your@address',
                        Subject => 'Here is the information you requested',
                ],
                body => $html,
                text_body => $plain_text #<--
        );

If you want your images to remain as links (rather than be embedded in the email) disable the "embed" option:

        my $email = Email::MIME->create_html(
                header => [
                        From => 'my@address',
                        To => 'your@address',
                        Subject => 'My speedy HTML',
                ],
                body => $html,
                embed => 0 #<--
        );

Optimising out HTML parsing

By default, the HTML is parsed to look for objects and stylesheets that need embedding. If you are controlling the construction of the HTML yourself, you can use Content Ids as the URIs within your HTML and then pass in a set of objects to associate with those Content IDs:

        my $html = qq{
                <html><head><title>My Document</title></head><body>
                        <p>Here is a picture:</p><img src="cid:some_image_jpg@bbc.co.uk">
                </body></html>  
        };

You then need to create a mapping of the Content IDs to object filenames:

        my %objects = (
                "some_image_jpg@bbc.co.uk" => "/var/html/some_image.jpg"
        );

Finally you need to disable both the "embed" and "inline_css" options to turn off HTML parsing, and pass in your mapping:

        my $quick_to_assemble_mime = Email::MIME->create_html(
                header => [
                        From => 'my@address',
                        To => 'your@address',
                        Subject => 'My speedy HTML',
                ],
                body => $html,
                embed => 0,          #<--
                inline_css => 0,     #<--
                objects => \%objects #<--
        );

Preprocessing templates

If you have for example a personalised newsletter where your HTML will vary slightly from one email to the next, but you don't want to re-parse the HTML each time to re-fetch and attach objects, you can use the "embed_objects" function to pre-process the template, converting URIs into CIDs:

        use Email::MIME::CreateHTML qw(embed_objects);
        my ($preproc_tmpl_content, $cid_mapping) = embed_objects($tmpl_content);

You can then reuse this and the CID mapping:

        my $template = compile_template($preproc_tmpl_content);
        foreach $newsletter (@newsletters) {
                
                #Do templating
                my $html = $template->process($newsletter);
                
                #Build MIME structure
                my $mime = Email::MIME->create_html(
                        header => [
                                From => $reply_address,
                                To => $newsletter->address,
                                Subject => 'Weekly newsletter',
                        ],
                        body => $html,
                        embed => 0,              #Already done
                        inline_css => 0,         #Already done
                        objects => $cid_mapping  #Here's one we prepared earlier
                );
                
                #Send email
                send_email($mime);
        }

Note that one caveat with this approach is that all possible images that might be used in the template will be attached to the email. Depending on your template logic, it may be that some are never actually referenced from within the email (e.g. if an image is conditionally displayed) so this may create unnecessarily large emails.

Plugging in a custom resource resolver

A custom resource resolver can be specified by passing your own object to resolver:

        my $mime = Email::MIME->create_html(
                header => [
                        From => 'my@address',
                        To => 'your@address',
                        Subject => 'Here is the information you requested',
                ],
                body => $html,
                base => 'http://internal.foo.co.uk/images/',
                resolver => new MyResolver,         #<--
        );

The object needs to have the following API:

        package MyResolver;
        sub new {
                my ($self, $options) = @_;
                my $base_uri = $options->{base};
                #... YOUR CODE HERE ... (probably want to stash $base_uri in $self)
        }

        sub get_resource {
                my ($self, $uri) = @_;
                my ($content,$filename,$mimetype,$xfer_encoding);
                #... YOUR CODE HERE ...
                return ($content,$filename,$mimetype,$xfer_encoding);                   
        }

where:

        $uri is the URI of the object we are embedding (taken from the markup or passed in via the CID mapping)
        $base_uri is base URI used to resolve relative URIs
        
        $content is a scalar containing the contents of the file
        $filename is used to set the name attribute of the Email::MIME object
        $mimetype is used to set the content_type attribute of the Email::MIME object
        $xfer_encoding is used to set the encoding attribute of the Email::MIME object
        (note this is the suitable transfer encoding NOT a character encoding)

Plugging in different types of object cache

You can use a cache from the Cache::Cache distribution:

        use Cache::MemoryCache;
        my $mime = Email::MIME->create_html(
                header => \@headers,
                body => $html,
                object_cache => new Cache::MemoryCache( { 
                        'namespace' => 'MyNamespace',
                        'default_expires_in' => 600 
                } )
        );

Or a cache from the Cache distribution:

        use Cache::File;
        my $mime = Email::MIME->create_html(
                header => \@headers,
                body => $html,
                object_cache => Cache::File->new( 
                        cache_root => '/tmp/mycache',
                        default_expires => '600 sec'
                )
        );

Alternatively you can roll your own. You just need to define an object with get and set methods:

        my $mime = Email::MIME->create_html(
                header => \@headers,
                body => $html,
                object_cache => new MyCache() 
        );
        
        package MyCache;        
        our %Cache;
        sub new {return bless({}, shift())}
        sub get {return $Cache{shift()}}
        sub set {$Cache{shift()} = shift()}
        1;

TODO

Maybe add option to control the order that the text + html parts appear in the MIME message.

AUTHOR

Tony Hennessy and Simon Flack with cookbook + some refactoring by John Alden <cpan _at_ bbc _dot_ co _dot_ uk> with additional contributions by Ricardo Signes <rjbs@cpan.org> and Henry Van Styn <vanstyn@cpan.org>

COPYRIGHT

See the file COPYING in this distribution, or http://www.gnu.org/licenses/gpl.txt