diff --git a/lib/tasks/2017_12_21_replace_deprecated_mail_template_tags.rake b/lib/tasks/2017_12_21_replace_deprecated_mail_template_tags.rake
new file mode 100644
index 000000000..18212003f
--- /dev/null
+++ b/lib/tasks/2017_12_21_replace_deprecated_mail_template_tags.rake
@@ -0,0 +1,22 @@
+namespace :'2017_12_21_replace_deprecated_mail_template_tags' do
+  task set: :environment do
+    replace_tag('numero_dossier', 'numéro du dossier')
+    replace_tag('date_de_decision', 'date de décision')
+    replace_tag('libelle_procedure', 'libellé procédure')
+    replace_tag('lien_dossier', 'lien dossier')
+  end
+
+  def replace_tag(old_tag, new_tag)
+    mails = [ Mails::ClosedMail, Mails::InitiatedMail, Mails::ReceivedMail, Mails::RefusedMail, Mails::WithoutContinuationMail]
+    mails.each do |mail|
+      replace_tag_in(mail, 'object', old_tag, new_tag)
+      replace_tag_in(mail, 'body', old_tag, new_tag)
+    end
+  end
+
+  def replace_tag_in(mail, field, old_tag, new_tag)
+    mail
+      .where("#{field} LIKE ?", "%#{old_tag}%")
+      .update_all("#{field} = REPLACE(#{field}, '#{old_tag}', '#{new_tag}')")
+  end
+end