Problem
You want to send emails from a Ruby on Rails application, when there is a specific condition on a database table. If the database table gets modified by another application outside Rails you cannot use an observer model.

Solution
We already assume that:

• You are using a database
• You have a model named voicemail (id, number_id, audio, created_at, updated_at)
• You have a model named number (id, voicemail_email_set, voicemail_email, ….)
• A mail server to use (smtp in our case)
• Another application (voice application) populates the voicemail table but with empty updated_at values

So the steps we have to follow are:

1. Change the settings in your config/environment.rb file to use the settings for your mail server, and make sure you restart your application after the changes:

   ActionMailer::Base.smtp_settings = {
     :address        => "yourmailserver.com",
     :port           =>  25,
     :domain         => "your.domain.com",
     :authentication => :login,
     :user_name      => "your_smtp_username",
     :password       => "your_smtp_password",
     :raise_delivery_errors  => true}

2. Create your mailer model (ie voicemail_mailer.rb), in app/models:

   class VoicemailMailer < ActionMailer::Base
      # We need the open-uri to be able to open url *** if the file to attach is in an http location ***
     require 'open-uri'
    
     def sent(email_to,email_from,email_subject,email_body,voicemail_to_send)
       # Check to see if we have a file for the email body message
       @subject    = email_subject
       @body       = email_body
       @recipients = email_to
       @from       = email_from
       @sent_on    = Time.now
       
       # Split the file in directory and filename
       file_path = File.split(voicemail_to_send)
       file_dir  = file_path[0]
       file_name = file_path[1]
       
       # Get the file
       tmp_file = open(voicemail_to_send).read
       
       part( :content_type => "application/wav", 
             :disposition => "attachment; filename=#{file_name}", 
             :transfer_encoding => "base64") do |attachment|
               attachment.body = tmp_file
       end
     end
   end
   

3. Create your email scheduler in file lib/email_scheduler.rb:

   #!/usr/bin/env /path_to_your_app/script/runner
   
   # get all the voicemails that have not been sent yet 
   voicemails_to_email = VoiceMail.find(:all, :conditions => 'updated_at is null')
   
   # For all the voicemails we have, send them and update the field date_sent
   for vm2email in voicemails_to_email do
     # Get the number for the voicemail
     number = Number.find(vm2email.number_id)
     
     # check to see if the send to email is set for the number
     if number.voicemail_email_set
       # Get number details (email_to,email_from etc)
       email_to          = number.voicemail_email
       voicemail_to_send = vm2email.audio
       # Set other details
       email_from      = 'Service@yourdomain.com'
       email_subject   = 'Please find attached your voicemail message'
       email_body      = "Received on: #{Time.now} \n for number: #{number.phone_no}"
   
       # Now send the email
       VoicemailMailer.deliver_sent(email_to,email_from,email_subject,email_body,voicemail_to_send)
   
       # And update the record's date_sent field
       vm2email.updated_at = Time.now
       vm2email.save
     end
   end
   

4. Create a task in your crontab that runs the scheduler (every five minutes):

   0,5,10,15,20,25,30,35,40,45,50,55 * * * * path_to_your_ror_app/lib/email_scheduler.rb