diff --git a/app/validators/email_mx_validator.rb b/app/validators/email_mx_validator.rb
index 5b4c684b2c..96fbedcfcf 100644
--- a/app/validators/email_mx_validator.rb
+++ b/app/validators/email_mx_validator.rb
@@ -24,6 +24,7 @@ class EmailMxValidator < ActiveModel::Validator
 
       ([domain] + hostnames).uniq.each do |hostname|
         ips.concat(dns.getresources(hostname, Resolv::DNS::Resource::IN::A).to_a.map { |e| e.address.to_s })
+        ips.concat(dns.getresources(hostname, Resolv::DNS::Resource::IN::AAAA).to_a.map { |e| e.address.to_s })
       end
     end
 
diff --git a/spec/validators/email_mx_validator_spec.rb b/spec/validators/email_mx_validator_spec.rb
index bc68f63cfb..48e17a4f10 100644
--- a/spec/validators/email_mx_validator_spec.rb
+++ b/spec/validators/email_mx_validator_spec.rb
@@ -11,6 +11,7 @@ describe EmailMxValidator do
 
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::MX).and_return([])
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
       allow(resolver).to receive(:timeouts=).and_return(nil)
       allow(Resolv::DNS).to receive(:open).and_yield(resolver)
 
@@ -23,7 +24,9 @@ describe EmailMxValidator do
 
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::MX).and_return([double(exchange: 'mail.example.com')])
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
       allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
       allow(resolver).to receive(:timeouts=).and_return(nil)
       allow(Resolv::DNS).to receive(:open).and_yield(resolver)
 
@@ -37,6 +40,21 @@ describe EmailMxValidator do
 
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::MX).and_return([])
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::A).and_return([double(address: '1.2.3.4')])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
+      allow(resolver).to receive(:timeouts=).and_return(nil)
+      allow(Resolv::DNS).to receive(:open).and_yield(resolver)
+
+      subject.validate(user)
+      expect(user.errors).to have_received(:add)
+    end
+
+    it 'adds an error if the AAAA record is blacklisted' do
+      EmailDomainBlock.create!(domain: 'fd00::1')
+      resolver = double
+
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::MX).and_return([])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::AAAA).and_return([double(address: 'fd00::1')])
       allow(resolver).to receive(:timeouts=).and_return(nil)
       allow(Resolv::DNS).to receive(:open).and_yield(resolver)
 
@@ -50,7 +68,25 @@ describe EmailMxValidator do
 
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::MX).and_return([double(exchange: 'mail.example.com')])
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
       allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::A).and_return([double(address: '2.3.4.5')])
+      allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
+      allow(resolver).to receive(:timeouts=).and_return(nil)
+      allow(Resolv::DNS).to receive(:open).and_yield(resolver)
+
+      subject.validate(user)
+      expect(user.errors).to have_received(:add)
+    end
+
+    it 'adds an error if the MX IPv6 record is blacklisted' do
+      EmailDomainBlock.create!(domain: 'fd00::2')
+      resolver = double
+
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::MX).and_return([double(exchange: 'mail.example.com')])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
+      allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::AAAA).and_return([double(address: 'fd00::2')])
       allow(resolver).to receive(:timeouts=).and_return(nil)
       allow(Resolv::DNS).to receive(:open).and_yield(resolver)
 
@@ -64,7 +100,9 @@ describe EmailMxValidator do
 
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::MX).and_return([double(exchange: 'mail.example.com')])
       allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::A).and_return([])
+      allow(resolver).to receive(:getresources).with('example.com', Resolv::DNS::Resource::IN::AAAA).and_return([])
       allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::A).and_return([double(address: '2.3.4.5')])
+      allow(resolver).to receive(:getresources).with('mail.example.com', Resolv::DNS::Resource::IN::AAAA).and_return([double(address: 'fd00::2')])
       allow(resolver).to receive(:timeouts=).and_return(nil)
       allow(Resolv::DNS).to receive(:open).and_yield(resolver)