diff --git a/app/models/user.rb b/app/models/user.rb
index f44295d3..199ccd54 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -28,7 +28,7 @@ class User < ActiveRecord::Base
   validates :username, :email, presence: true
   validates :username, uniqueness: true, if: :username?
   validates :username, length: { in: 3..30 }, allow_nil: true
-  validates :email, format: { with: /@/ }, uniqueness: true, if: :email?, on: :create
+  validates :email, format: { with: /@/ }, uniqueness: true
   validates :url, format: URI::regexp(%w(http https)), allow_nil: true, allow_blank: true, on: :create
 
   has_many :devices, foreign_key: 'owner_id', after_add: :update_cached_device_ids!, after_remove: :update_cached_device_ids!
diff --git a/lib/tasks/pgsequences.rake b/lib/tasks/pgsequences.rake
deleted file mode 100644
index adf01c30..00000000
--- a/lib/tasks/pgsequences.rake
+++ /dev/null
@@ -1,9 +0,0 @@
-namespace :pgsequences do
-  desc "Reset all Postgres sequences"
-  task :reset => :environment do
-    ActiveRecord::Base.connection.tables.each do |t|
-      ActiveRecord::Base.connection.reset_pk_sequence!(t)
-      puts "Reset pk sequence on table: #{t}"
-    end
-  end
-end
diff --git a/lib/tasks/users.rake b/lib/tasks/users.rake
new file mode 100644
index 00000000..d1e8ae8f
--- /dev/null
+++ b/lib/tasks/users.rake
@@ -0,0 +1,55 @@
+namespace :users do
+    task :remove_null_emails => :environment do
+        team_user = User.find_by_email("team@pral2a.com")
+        count_team_devices = team_user.devices.length
+        count_users = User.count
+        count_moved_devices = 0
+        count_deleted_users = 0
+        User.where("email IS NULL or trim(email) = ''").each do |user|
+            puts "user #{user.id} (#{user.username}) has blank email, moving devices to team account:"
+            user.devices.each do |device|
+                device.owner = team_user
+                device.save(validate: false)
+                count_team_devices += 1
+                count_moved_devices += 1
+                puts "\t - Device #{device.id} moved to user: #{team_user.id}"
+            end
+            user.destroy!
+            count_users -= 1
+            count_deleted_users += 1
+        end
+        puts "Check moved devices: #{team_user.reload.devices.length} (should be #{count_team_devices}, #{count_moved_devices} moved)"
+        puts "Check remaining users: #{User.count} (should be #{count_users}, #{count_deleted_users} deleted)"
+    end
+
+    task :deduplicate_emails => :environment do
+        count_deleted_users = 0
+        count_users = User.count
+        count_devices = Device.count
+        count_moved_devices = 0
+        ActiveRecord::Base.connection.execute(
+            "SELECT email FROM users GROUP BY email HAVING count(id) > 1"
+        ).each do |record|
+            email = record["email"]
+            users = User.where(email: email).to_a
+            puts "Found #{users.length} users for email: #{email}: (#{users.map(&:id).join(",")})"
+            move_to_user = users.shift
+            puts " - Moving devices from users (#{users.map(&:id).join(",")}) to user #{move_to_user.id}"
+            users.each do |user|
+                user.devices.each do |device|
+                    device.owner = move_to_user
+                    device.save(validate: false)
+                    count_moved_devices += 1
+                    puts "  - Moved device #{device.id} to user: #{move_to_user.id}"
+                end
+            end
+            puts " - Deleting users: #{users.map(&:id).join(",")}"
+            users.each do |user|
+                user.destroy!
+                count_deleted_users += 1
+            end
+        end
+        puts "Check moved devices: #{Device.count} (should be #{count_devices}, #{count_moved_devices} moved)"
+        puts "Check deleted users: #{User.count} (should be #{count_users - count_deleted_users}, #{count_deleted_users} deleted)"
+    end
+end
\ No newline at end of file
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 07fa099d..fafe6ae7 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -34,6 +34,19 @@
     expect(build(:user, avatar: 'http://i.imgur.com/SZD8ADL.JPEG')).to be_valid
   end
 
+  it "is invalid with an email which isn't an email adddress" do
+    expect(build(:user, email: "not an email")).to be_invalid
+  end
+
+  it "is invalid without an email" do
+    expect(build(:user, email: nil)).to be_invalid
+  end
+
+  it "is invalid with an email which is already taken" do
+    create(:user, email: "taken@example.com")
+    expect(build(:user, email: "taken@example.com")).to be_invalid
+  end
+
   it "has a location" do
     user = create(:user, country_code: 'es', city: 'Barcelona')
     expect(user.country.to_s).to eq("Spain")