Multipart Alternative + Multipart Related Email with ActionMailer for Rails 3

Since the first post on this topic, I have migrated my app from Rails 2.3.11 to Rails 3.0.6. See the first post if you still need the solution for Rails 2.

I had a need at work to send email out of our Rails application which met the following criteria:

• It has both a plain text and HTML part.
• It may have embedded images in the HTML part.
• It may have attachments.

Below is the code, which you can put in your app/models directory.

class EmbeddedMailer < ActionMailer::Base

  def embedded_mail(to, from, subject, html_message, text_message, files = {}, embeds = {})
    mail(:to => to, :from => from, :subject => subject) do |format|
      format.text { render :text => text_message }
      format.html { render :text => html_message }
    end

    # Embeds
    embeds.each do |key, embed|
      attachments.inline[key] = {
        :content => File.read(embed[:path]),
        :content_id => "<#{key}>"
      }
    end

    # Attachments
    files.each do |key, embed|
      attachments[key] = File.read(embed[:path])
    end
  end

end

A Quick Explanation

Rails 3 has made this a lot easier. The only real hack is handling dynamic inline Content-ID’s. ActionMailer will dynamically generate a Content-ID for each inline attachment. We override that with the :content_id => "<#{key}>" line. The brackets are required.

The format of the files and embeds hashes is as follows. The key is the file name of the attached file. The value is another hash with content_type set to the content type of the attachment and path is the full path to the file. For example:

{ 'image.png' =>
    'content_type' => 'image/png',
    'path' => '/tmp/image.png'
}