diff --git a/app/forms/register_user_email_form.rb b/app/forms/register_user_email_form.rb
index 1a57677eebc..85706e9900a 100644
--- a/app/forms/register_user_email_form.rb
+++ b/app/forms/register_user_email_form.rb
@@ -25,10 +25,26 @@ def user
     @user ||= User.new
   end
 
+  def rate_limited?
+    @rate_limited
+  end
+
   def email
     email_address&.email
   end
 
+  def email_fingerprint
+    email_address&.email_fingerprint
+  end
+
+  def normalized_email
+    @normalized_email ||= EmailNormalizer.new(email).normalized_email
+  end
+
+  def digested_base_email
+    @digested_base_email ||= OpenSSL::Digest::SHA256.hexdigest(normalized_email)
+  end
+
   def validate_terms_accepted
     return if @terms_accepted || email_address_record&.user&.accepted_terms_at.present?
 
@@ -93,13 +109,7 @@ def process_successful_submission(request_id, instructions)
     elsif email_taken?
       send_sign_up_confirmed_email
     else
-      user.accepted_terms_at = Time.zone.now
-      user.save!
-      SendSignUpEmailConfirmation.new(user).call(
-        request_id: email_request_id(request_id),
-        instructions: instructions,
-        password_reset_requested: password_reset_requested?,
-      )
+      send_sign_up_email(request_id, instructions)
     end
   end
 
@@ -114,16 +124,46 @@ def extra_analytics_attributes
       email_already_exists: email_taken?,
       user_id: user.uuid || existing_user.uuid,
       domain_name: email&.split('@')&.last,
-      rate_limited: @rate_limited,
+      rate_limited: rate_limited?,
     }
   end
 
-  def send_sign_up_unconfirmed_email(request_id)
-    rate_limiter = RateLimiter.new(user: existing_user, rate_limit_type: :reg_unconfirmed_email)
+  def rate_limit!(rate_limit_type)
+    rate_limiter = RateLimiter.new(
+      target: digested_base_email,
+      rate_limit_type: rate_limit_type,
+    )
+
     rate_limiter.increment!
     @rate_limited = rate_limiter.limited?
+  end
+
+  def send_sign_up_email(request_id, instructions)
+    rate_limit!(:reg_unconfirmed_email)
+
+    if rate_limited?
+      @analytics.rate_limit_reached(
+        limiter_type: :reg_unconfirmed_email,
+      )
+      @attempts_tracker.user_registration_email_submission_rate_limited(
+        email: email, email_already_registered: false,
+      )
+    else
+      user.accepted_terms_at = Time.zone.now
+      user.save!
+
+      SendSignUpEmailConfirmation.new(user).call(
+        request_id: email_request_id(request_id),
+        instructions: instructions,
+        password_reset_requested: password_reset_requested?,
+      )
+    end
+  end
 
-    if @rate_limited
+  def send_sign_up_unconfirmed_email(request_id)
+    rate_limit!(:reg_unconfirmed_email)
+
+    if rate_limited?
       @analytics.rate_limit_reached(
         limiter_type: :reg_unconfirmed_email,
       )
@@ -136,11 +176,9 @@ def send_sign_up_unconfirmed_email(request_id)
   end
 
   def send_sign_up_confirmed_email
-    rate_limiter = RateLimiter.new(user: existing_user, rate_limit_type: :reg_confirmed_email)
-    rate_limiter.increment!
-    @rate_limited = rate_limiter.limited?
+    rate_limit!(:reg_confirmed_email)
 
-    if @rate_limited
+    if rate_limited?
       @analytics.rate_limit_reached(
         limiter_type: :reg_confirmed_email,
       )
@@ -166,8 +204,8 @@ def user_unconfirmed?
 
   def email_address_record
     return @email_address_record if defined?(@email_address_record)
+
     @email_address_record = EmailAddress.find_with_email(email)
-    @email_address_record
   end
 
   def existing_user
@@ -180,6 +218,7 @@ def email_request_id(request_id)
 
   def blocked_email_address
     return @blocked_email_address if defined?(@blocked_email_address)
-    @blocked_email_address = SuspendedEmail.find_with_email(email)
+
+    @blocked_email_address = SuspendedEmail.find_with_email_digest(digested_base_email)
   end
 end
diff --git a/app/models/suspended_email.rb b/app/models/suspended_email.rb
index 5a1011bc884..ac46081b80f 100644
--- a/app/models/suspended_email.rb
+++ b/app/models/suspended_email.rb
@@ -18,5 +18,9 @@ def create_from_email_address!(email_address)
     def find_with_email(email)
       find_by(digested_base_email: generate_email_digest(email))&.email_address
     end
+
+    def find_with_email_digest(digest)
+      find_by(digested_base_email: digest)&.email_address
+    end
   end
 end
diff --git a/app/services/email_normalizer.rb b/app/services/email_normalizer.rb
index acfac75488a..4c298cbe8cb 100644
--- a/app/services/email_normalizer.rb
+++ b/app/services/email_normalizer.rb
@@ -28,6 +28,7 @@ def gmail?
 
   def google_mx_record?
     return false if ENV['RAILS_OFFLINE']
+    return false if email.domain.blank? || !email.domain.to_s.ascii_only?
 
     mx_records(email.domain).any? { |domain| domain.end_with?('google.com') }
   end
diff --git a/spec/features/visitors/sign_up_with_email_spec.rb b/spec/features/visitors/sign_up_with_email_spec.rb
index ee559e7d763..409b324821f 100644
--- a/spec/features/visitors/sign_up_with_email_spec.rb
+++ b/spec/features/visitors/sign_up_with_email_spec.rb
@@ -72,14 +72,16 @@
     sign_up_with(email)
 
     starting_count = unread_emails_for(email).size
-    max_attempts = IdentityConfig.store.reg_unconfirmed_email_max_attempts
-    (max_attempts - 1).times do |i|
+    remaining_attempts = IdentityConfig.store.
+      reg_unconfirmed_email_max_attempts - 1 - starting_count
+
+    1.upto(remaining_attempts) do |i|
       sign_up_with(email)
-      expect(unread_emails_for(email).size).to eq(starting_count + i + 1)
+      expect(unread_emails_for(email).size).to eq(starting_count + i)
     end
 
-    expect(unread_emails_for(email).size).to eq(starting_count + max_attempts - 1)
+    expect(unread_emails_for(email).size).to eq(starting_count + remaining_attempts)
     sign_up_with(email)
-    expect(unread_emails_for(email).size).to eq(starting_count + max_attempts - 1)
+    expect(unread_emails_for(email).size).to eq(starting_count + remaining_attempts)
   end
 end
diff --git a/spec/forms/register_user_email_form_spec.rb b/spec/forms/register_user_email_form_spec.rb
index 60fa95cbb96..495751d73a8 100644
--- a/spec/forms/register_user_email_form_spec.rb
+++ b/spec/forms/register_user_email_form_spec.rb
@@ -8,8 +8,10 @@
   it_behaves_like 'email validation'
 
   describe '#submit' do
+    let(:anonymous_uuid) { 'anonymous-uuid' }
     let(:email_domain) { 'gmail.com' }
     let(:registered_email_address) { 'taken@' + email_domain }
+    let(:variation_of_preexisting_email) { 'TAKEN@' + email_domain }
     let(:unregistered_email_address) { 'not_taken@' + email_domain }
     let(:registered_and_confirmed_user) do
       [:user, :fully_registered, **{ email: registered_email_address }]
@@ -94,7 +96,6 @@
       end
     end
 
-    let(:variation_of_preexisting_email) { 'TAKEN@' + email_domain }
     context 'when email is already taken' do
       let!(:existing_user) { create(*registered_and_confirmed_user) }
       let(:extra_params) do
@@ -191,6 +192,30 @@
           limiter_type: :reg_unconfirmed_email,
         )
       end
+
+      context 'with the same normalized email address' do
+        let(:rate_limit) { IdentityConfig.store.reg_unconfirmed_email_max_attempts }
+
+        it 'creates rate_limiter events after reaching rate_limiter limit' do
+          expect(attempts_tracker).to receive(
+            :user_registration_email_submission_rate_limited,
+          ).with(
+            email: "taken+#{rate_limit}@gmail.com", email_already_registered: false,
+          )
+
+          1.upto(rate_limit) do |i|
+            RegisterUserEmailForm.new(analytics: analytics, attempts_tracker: attempts_tracker).
+              submit(
+                email: "taken+#{i}@gmail.com", terms_accepted: '1',
+              )
+          end
+
+          expect(analytics).to have_logged_event(
+            'Rate Limit Reached',
+            limiter_type: :reg_unconfirmed_email,
+          )
+        end
+      end
     end
 
     context 'when the email exists but is unconfirmed and on a confirmed user' do
@@ -240,9 +265,32 @@
 
         expect(User.find_with_email(unregistered_email_address).email_language).to eq('fr')
       end
+
+      context 'with the same normalized email address' do
+        let(:rate_limit) { IdentityConfig.store.reg_unconfirmed_email_max_attempts }
+
+        it 'creates rate_limiter events after reaching rate_limiter limit' do
+          expect(attempts_tracker).to receive(
+            :user_registration_email_submission_rate_limited,
+          ).with(
+            email: "taken+#{rate_limit}@gmail.com", email_already_registered: false,
+          )
+
+          1.upto(rate_limit) do |i|
+            RegisterUserEmailForm.new(analytics: analytics, attempts_tracker: attempts_tracker).
+              submit(
+                email: "taken+#{i}@gmail.com", terms_accepted: '1',
+              )
+          end
+
+          expect(analytics).to have_logged_event(
+            'Rate Limit Reached',
+            limiter_type: :reg_unconfirmed_email,
+          )
+        end
+      end
     end
 
-    let(:anonymous_uuid) { 'anonymous-uuid' }
     context 'when email is invalid' do
       it 'returns false and adds errors to the form object' do
         invalid_email = 'invalid_email'
diff --git a/spec/models/suspended_email_spec.rb b/spec/models/suspended_email_spec.rb
index bfb06ec4002..c03d1587298 100644
--- a/spec/models/suspended_email_spec.rb
+++ b/spec/models/suspended_email_spec.rb
@@ -41,4 +41,29 @@
       end
     end
   end
+
+  describe '.find_with_email_digest' do
+    context 'when the email is not blocked' do
+      it 'returns nil' do
+        email = 'not_blocked@example.com'
+        digested_base_email = Digest::SHA256.hexdigest(email)
+
+        expect(SuspendedEmail.find_with_email_digest(digested_base_email)).to be_nil
+      end
+    end
+
+    context 'when the email is blocked' do
+      it 'returns the original email address' do
+        blocked_email = FactoryBot.create(:email_address, email: 'blocked@example.com')
+        digested_base_email = Digest::SHA256.hexdigest('blocked@example.com')
+        FactoryBot.create(
+          :suspended_email,
+          digested_base_email: digested_base_email,
+          email_address: blocked_email,
+        )
+
+        expect(SuspendedEmail.find_with_email_digest(digested_base_email)).to eq(blocked_email)
+      end
+    end
+  end
 end
diff --git a/spec/services/email_normalizer_spec.rb b/spec/services/email_normalizer_spec.rb
index 0afa8b6c529..53c20e7a286 100644
--- a/spec/services/email_normalizer_spec.rb
+++ b/spec/services/email_normalizer_spec.rb
@@ -6,6 +6,22 @@
   describe '#normalized_email' do
     subject(:normalized_email) { normalizer.normalized_email }
 
+    context 'when email is nil' do
+      let(:email) { nil }
+
+      it 'is an empty string' do
+        expect(normalized_email).to eq(email.to_s)
+      end
+    end
+
+    context 'with an invalid email' do
+      let(:email) { 'invalid_email' }
+
+      it 'is the same string' do
+        expect(normalized_email).to eq(email)
+      end
+    end
+
     context 'with a non-gmail domain' do
       let(:email) { 'foobar+123@example.com' }
 
@@ -57,5 +73,16 @@
         end
       end
     end
+
+    context 'with an internationalized domain name' do
+      let(:email) { 'test+1@çà.com' }
+      let(:rails_offline) { false }
+
+      before { stub_const('ENV', 'RAILS_OFFLINE' => (rails_offline ? 'TRUE' : nil)) }
+
+      it 'is the same email' do
+        expect(normalized_email).to eq(email)
+      end
+    end
   end
 end