diff --git a/app/assets/javascripts/discourse/app/controllers/create-account.js b/app/assets/javascripts/discourse/app/controllers/create-account.js
index 198dbe92a8c..adbebd4227c 100644
--- a/app/assets/javascripts/discourse/app/controllers/create-account.js
+++ b/app/assets/javascripts/discourse/app/controllers/create-account.js
@@ -5,7 +5,7 @@ import discourseComputed, {
   on,
 } from "discourse-common/utils/decorators";
 import { A } from "@ember/array";
-import EmberObject from "@ember/object";
+import EmberObject, { action } from "@ember/object";
 import I18n from "I18n";
 import ModalFunctionality from "discourse/mixins/modal-functionality";
 import NameValidation from "discourse/mixins/name-validation";
@@ -17,6 +17,7 @@ import UsernameValidation from "discourse/mixins/username-validation";
 import { ajax } from "discourse/lib/ajax";
 import { emailValid } from "discourse/lib/utilities";
 import { findAll } from "discourse/models/login-method";
+import discourseDebounce from "discourse-common/lib/debounce";
 import getURL from "discourse-common/lib/get-url";
 import { isEmpty } from "@ember/utils";
 import { notEmpty } from "@ember/object/computed";
@@ -58,6 +59,8 @@ export default Controller.extend(
         accountEmail: "",
         accountUsername: "",
         accountPassword: "",
+        serverAccountEmail: null,
+        serverEmailValidation: null,
         authOptions: null,
         complete: false,
         formSubmitted: false,
@@ -130,13 +133,27 @@ export default Controller.extend(
     },
 
     // Check the email address
-    @discourseComputed("accountEmail", "rejectedEmails.[]")
-    emailValidation(email, rejectedEmails) {
+    @discourseComputed(
+      "serverAccountEmail",
+      "serverEmailValidation",
+      "accountEmail",
+      "rejectedEmails.[]"
+    )
+    emailValidation(
+      serverAccountEmail,
+      serverEmailValidation,
+      email,
+      rejectedEmails
+    ) {
       const failedAttrs = {
         failed: true,
         element: document.querySelector("#new-account-email"),
       };
 
+      if (serverAccountEmail === email && serverEmailValidation) {
+        return serverEmailValidation;
+      }
+
       // If blank, fail without a reason
       if (isEmpty(email)) {
         return EmberObject.create(
@@ -146,7 +163,7 @@ export default Controller.extend(
         );
       }
 
-      if (rejectedEmails.includes(email)) {
+      if (rejectedEmails.includes(email) || !emailValid(email)) {
         return EmberObject.create(
           Object.assign(failedAttrs, {
             reason: I18n.t("user.email.invalid"),
@@ -168,18 +185,48 @@ export default Controller.extend(
         });
       }
 
-      if (emailValid(email)) {
-        return EmberObject.create({
-          ok: true,
-          reason: I18n.t("user.email.ok"),
-        });
+      return EmberObject.create({
+        ok: true,
+        reason: I18n.t("user.email.ok"),
+      });
+    },
+
+    @action
+    checkEmailAvailability() {
+      if (
+        !this.emailValidation.ok ||
+        this.serverAccountEmail === this.accountEmail
+      ) {
+        return;
       }
 
-      return EmberObject.create(
-        Object.assign(failedAttrs, {
-          reason: I18n.t("user.email.invalid"),
+      return User.checkEmail(this.accountEmail)
+        .then((result) => {
+          if (result.failed) {
+            this.setProperties({
+              serverAccountEmail: this.accountEmail,
+              serverEmailValidation: EmberObject.create({
+                failed: true,
+                element: document.querySelector("#new-account-email"),
+                reason: result.errors[0],
+              }),
+            });
+          } else {
+            this.setProperties({
+              serverAccountEmail: this.accountEmail,
+              serverEmailValidation: EmberObject.create({
+                ok: true,
+                reason: I18n.t("user.email.ok"),
+              }),
+            });
+          }
         })
-      );
+        .catch(() => {
+          this.setProperties({
+            serverAccountEmail: null,
+            serverEmailValidation: null,
+          });
+        });
     },
 
     @discourseComputed(
@@ -220,7 +267,7 @@ export default Controller.extend(
         // If email is valid and username has not been entered yet,
         // or email and username were filled automatically by 3rd parth auth,
         // then look for a registered username that matches the email.
-        this.fetchExistingUsername();
+        discourseDebounce(this, this.fetchExistingUsername, 500);
       }
     },
 
diff --git a/app/assets/javascripts/discourse/app/mixins/username-validation.js b/app/assets/javascripts/discourse/app/mixins/username-validation.js
index 54d20cb3cd1..b8f14bc818d 100644
--- a/app/assets/javascripts/discourse/app/mixins/username-validation.js
+++ b/app/assets/javascripts/discourse/app/mixins/username-validation.js
@@ -29,24 +29,18 @@ export default Mixin.create({
   minUsernameLength: setting("min_username_length"),
 
   fetchExistingUsername() {
-    discourseDebounce(
-      this,
-      function () {
-        User.checkUsername(null, this.accountEmail).then((result) => {
-          if (
-            result.suggestion &&
-            (isEmpty(this.accountUsername) ||
-              this.accountUsername === this.get("authOptions.username"))
-          ) {
-            this.setProperties({
-              accountUsername: result.suggestion,
-              prefilledUsername: result.suggestion,
-            });
-          }
+    User.checkUsername(null, this.accountEmail).then((result) => {
+      if (
+        result.suggestion &&
+        (isEmpty(this.accountUsername) ||
+          this.accountUsername === this.get("authOptions.username"))
+      ) {
+        this.setProperties({
+          accountUsername: result.suggestion,
+          prefilledUsername: result.suggestion,
         });
-      },
-      500
-    );
+      }
+    });
   },
 
   @observes("accountUsername")
@@ -55,7 +49,7 @@ export default Mixin.create({
 
     let result = this.basicUsernameValidation(accountUsername);
     if (result.shouldCheck) {
-      this.checkUsernameAvailability();
+      discourseDebounce(this, this.checkUsernameAvailability, 500);
     }
     this.set("usernameValidation", result);
   },
@@ -84,43 +78,37 @@ export default Mixin.create({
   },
 
   checkUsernameAvailability() {
-    discourseDebounce(
-      this,
-      function () {
-        return User.checkUsername(this.accountUsername, this.accountEmail).then(
-          (result) => {
-            this.set("isDeveloper", false);
-            if (result.available) {
-              if (result.is_developer) {
-                this.set("isDeveloper", true);
-              }
-              return this.set(
-                "usernameValidation",
-                validResult({ reason: I18n.t("user.username.available") })
-              );
-            } else {
-              if (result.suggestion) {
-                return this.set(
-                  "usernameValidation",
-                  failedResult({
-                    reason: I18n.t("user.username.not_available", result),
-                  })
-                );
-              } else {
-                return this.set(
-                  "usernameValidation",
-                  failedResult({
-                    reason: result.errors
-                      ? result.errors.join(" ")
-                      : I18n.t("user.username.not_available_no_suggestion"),
-                  })
-                );
-              }
-            }
+    return User.checkUsername(this.accountUsername, this.accountEmail).then(
+      (result) => {
+        this.set("isDeveloper", false);
+        if (result.available) {
+          if (result.is_developer) {
+            this.set("isDeveloper", true);
           }
-        );
-      },
-      500
+          return this.set(
+            "usernameValidation",
+            validResult({ reason: I18n.t("user.username.available") })
+          );
+        } else {
+          if (result.suggestion) {
+            return this.set(
+              "usernameValidation",
+              failedResult({
+                reason: I18n.t("user.username.not_available", result),
+              })
+            );
+          } else {
+            return this.set(
+              "usernameValidation",
+              failedResult({
+                reason: result.errors
+                  ? result.errors.join(" ")
+                  : I18n.t("user.username.not_available_no_suggestion"),
+              })
+            );
+          }
+        }
+      }
     );
   },
 });
diff --git a/app/assets/javascripts/discourse/app/models/user.js b/app/assets/javascripts/discourse/app/models/user.js
index 5f7892bee53..f0a0541bcea 100644
--- a/app/assets/javascripts/discourse/app/models/user.js
+++ b/app/assets/javascripts/discourse/app/models/user.js
@@ -1044,6 +1044,10 @@ User.reopenClass(Singleton, {
     });
   },
 
+  checkEmail(email) {
+    return ajax(userPath("check_email"), { data: { email } });
+  },
+
   groupStats(stats) {
     const responses = UserActionStat.create({
       count: 0,
diff --git a/app/assets/javascripts/discourse/app/templates/modal/create-account.hbs b/app/assets/javascripts/discourse/app/templates/modal/create-account.hbs
index f2b71839b36..fc5ccc83e64 100644
--- a/app/assets/javascripts/discourse/app/templates/modal/create-account.hbs
+++ b/app/assets/javascripts/discourse/app/templates/modal/create-account.hbs
@@ -25,7 +25,7 @@
                 {{#if emailValidated}}
                   <span class="value">{{accountEmail}}</span>
                 {{else}}
-                  {{input type="email" value=accountEmail id="new-account-email" name="email" class=(value-entered accountEmail) autofocus="autofocus"}}
+                  {{input type="email" value=accountEmail id="new-account-email" name="email" class=(value-entered accountEmail) autofocus="autofocus" focusOut=(action "checkEmailAvailability")}}
                   <label class="alt-placeholder" for="new-account-email">
                     {{i18n "user.email.title"}}
                     {{~#if userFields~}}
diff --git a/app/assets/javascripts/discourse/tests/helpers/create-pretender.js b/app/assets/javascripts/discourse/tests/helpers/create-pretender.js
index 5e88df36c41..419443e8325 100644
--- a/app/assets/javascripts/discourse/tests/helpers/create-pretender.js
+++ b/app/assets/javascripts/discourse/tests/helpers/create-pretender.js
@@ -449,6 +449,10 @@ export function applyDefaultHandlers(pretender) {
     return response({ available: true });
   });
 
+  pretender.get("/u/check_email", function () {
+    return response({ success: "OK" });
+  });
+
   pretender.post("/u", () => response({ success: true }));
 
   pretender.get("/login.html", () => [200, {}, "LOGIN PAGE"]);
diff --git a/app/controllers/users_controller.rb b/app/controllers/users_controller.rb
index 006fb58b7f2..c54018f89d3 100644
--- a/app/controllers/users_controller.rb
+++ b/app/controllers/users_controller.rb
@@ -34,6 +34,7 @@ class UsersController < ApplicationController
   #  once that happens you can't log in with social
   skip_before_action :verify_authenticity_token, only: [:create]
   skip_before_action :redirect_to_login_if_required, only: [:check_username,
+                                                            :check_email,
                                                             :create,
                                                             :account_created,
                                                             :activate_account,
@@ -522,6 +523,24 @@ class UsersController < ApplicationController
     render json: checker.check_username(username, email)
   end
 
+  def check_email
+    RateLimiter.new(nil, "check-email-#{request.remote_ip}", 10, 1.minute).performed!
+
+    if SiteSetting.hide_email_address_taken?
+      return render json: success_json
+    end
+
+    user_email = UserEmail.new(email: params[:email])
+
+    if user_email.valid?
+      render json: success_json
+    else
+      render json: failed_json.merge(errors: user_email.errors.full_messages)
+    end
+  rescue RateLimiter::LimitExceeded
+    render json: success_json
+  end
+
   def user_from_params_or_current_user
     params[:for_user_id] ? User.find(params[:for_user_id]) : current_user
   end
diff --git a/config/routes.rb b/config/routes.rb
index 65aa8444ac7..d8aff07d2b8 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -388,6 +388,7 @@ Discourse::Application.routes.draw do
       resources :users, except: [:index, :new, :show, :update, :destroy], path: root_path do
         collection do
           get "check_username"
+          get "check_email"
           get "is_local_username"
         end
       end
diff --git a/spec/requests/users_controller_spec.rb b/spec/requests/users_controller_spec.rb
index e0e7dda210e..2f8f5398e69 100644
--- a/spec/requests/users_controller_spec.rb
+++ b/spec/requests/users_controller_spec.rb
@@ -1584,6 +1584,30 @@ describe UsersController do
     end
   end
 
+  describe '#check_email' do
+    it 'returns success if hide_email_address_taken is true' do
+      SiteSetting.hide_email_address_taken = true
+
+      get "/u/check_email.json", params: { email: user.email }
+      expect(response.parsed_body["success"]).to be_present
+    end
+
+    it 'returns failure if email is not valid' do
+      get "/u/check_email.json", params: { email: "invalid" }
+      expect(response.parsed_body["failed"]).to be_present
+    end
+
+    it 'returns failure if email exists' do
+      get "/u/check_email.json", params: { email: user.email }
+      expect(response.parsed_body["failed"]).to be_present
+    end
+
+    it 'returns success if email does not exists' do
+      get "/u/check_email.json", params: { email: "available@example.com" }
+      expect(response.parsed_body["success"]).to be_present
+    end
+  end
+
   describe '#invited' do
     it 'fails for anonymous users' do
       user = Fabricate(:user)