Rename 'mail' model to 'email' in order to prevent 'Mail is not a module' error (which only shows in production).

app/models/contact.rb

@@ -1,4 +1,4 @@
 class Contact < ActiveRecord::Base
-  has_many :mails
+  has_many :emails
   has_many :phones
 end

app/models/email.rb

@@ -0,0 +1,3 @@
+class Email < ActiveRecord::Base
+  belongs_to :contact
+end

app/models/mail.rb

@@ -1,3 +0,0 @@
-class Mail < ActiveRecord::Base
-  belongs_to :contact
-end

db/migrate/20110515190518_create_emails.rb

@@ -0,0 +1,23 @@
+class CreateEmails < ActiveRecord::Migration
+  def self.up
+    create_table :emails do |t|
+      t.string :desc
+      t.string :address
+
+      t.timestamps
+    end
+
+    # we drop the 'mails' table as this is basically a renaming (without a need to migrate anything, yet)
+    drop_table :mails
+  end
+
+  def self.down
+    create_table :mails do |t|
+      t.string :desc
+      t.string :address
+      t.timestamps
+    end    
+
+    drop_table :emails
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20110514213956) do
+ActiveRecord::Schema.define(:version => 20110515190518) do
 
   create_table "contacts", :force => true do |t|
     t.string   "firstname"
@@ -24,7 +24,7 @@ ActiveRecord::Schema.define(:version => 20110514213956) do
     t.datetime "updated_at"
   end
 
-  create_table "mails", :force => true do |t|
+  create_table "emails", :force => true do |t|
     t.string   "desc"
     t.string   "address"
     t.datetime "created_at"

test/unit/email_test.rb

@@ -1,6 +1,6 @@
 require 'test_helper'
 
-class MailTest < ActiveSupport::TestCase
+class EmailTest < ActiveSupport::TestCase
   # Replace this with your real tests.
   test "the truth" do
     assert true