diff --git a/src/components/views/auth/RegistrationForm.js b/src/components/views/auth/RegistrationForm.js
index ad663bee47..cd3dab12ac 100644
--- a/src/components/views/auth/RegistrationForm.js
+++ b/src/components/views/auth/RegistrationForm.js
@@ -91,14 +91,25 @@ module.exports = React.createClass({
 
         const self = this;
         if (this.state.email == '') {
+            const haveIs = Boolean(this.props.serverConfig.isUrl);
+
+            let desc;
+            if (haveIs) {
+                desc = _t(
+                    "If you don't specify an email address, you won't be able to reset your password. " +
+                    "Are you sure?",
+                );
+            } else {
+                desc = _t(
+                    "No Identity Server is configured so you cannot add add an email address in order to " +
+                    "reset your password in the future.",
+                );
+            }
+
             const QuestionDialog = sdk.getComponent("dialogs.QuestionDialog");
             Modal.createTrackedDialog('If you don\'t specify an email address...', '', QuestionDialog, {
                 title: _t("Warning!"),
-                description:
-                    <div>
-                        { _t("If you don't specify an email address, you won't be able to reset your password. " +
-                            "Are you sure?") }
-                    </div>,
+                description: desc,
                 button: _t("Continue"),
                 onFinished: function(confirmed) {
                     if (confirmed) {
@@ -423,8 +434,16 @@ module.exports = React.createClass({
         });
     },
 
+    _showEmail() {
+        const haveIs = Boolean(this.props.serverConfig.isUrl);
+        if (!haveIs || !this._authStepIsUsed('m.login.email.identity')) {
+            return false;
+        }
+        return true;
+    },
+
     renderEmail() {
-        if (!this._authStepIsUsed('m.login.email.identity')) {
+        if (!this._showEmail()) {
             return null;
         }
         const Field = sdk.getComponent('elements.Field');
@@ -473,7 +492,8 @@ module.exports = React.createClass({
 
     renderPhoneNumber() {
         const threePidLogin = !SdkConfig.get().disable_3pid_login;
-        if (!threePidLogin || !this._authStepIsUsed('m.login.msisdn')) {
+        const haveIs = Boolean(this.props.serverConfig.isUrl);
+        if (!threePidLogin || !haveIs || !this._authStepIsUsed('m.login.msisdn')) {
             return null;
         }
         const CountryDropdown = sdk.getComponent('views.auth.CountryDropdown');
@@ -547,6 +567,19 @@ module.exports = React.createClass({
             <input className="mx_Login_submit" type="submit" value={_t("Register")} disabled={!this.props.canSubmit} />
         );
 
+        const emailHelperText = this._showEmail() ? <div>
+            {_t("Use an email address to recover your account.") + " "}
+            {_t("Other users can invite you to rooms using your contact details.")}
+        </div> : null;
+
+        const haveIs = Boolean(this.props.serverConfig.isUrl);
+        const noIsText = haveIs ? null : <div>
+            {_t(
+                "No Identity Server is configured: no email addreses can be added. " +
+                "You will be unable to reset your password.",
+            )}
+        </div>;
+
         return (
             <div>
                 <h3>
@@ -565,8 +598,8 @@ module.exports = React.createClass({
                         {this.renderEmail()}
                         {this.renderPhoneNumber()}
                     </div>
-                    {_t("Use an email address to recover your account.") + " "}
-                    {_t("Other users can invite you to rooms using your contact details.")}
+                    { emailHelperText }
+                    { noIsText }
                     { registerButton }
                 </form>
             </div>
diff --git a/src/components/views/auth/ServerConfig.js b/src/components/views/auth/ServerConfig.js
index 9dcc2c9abe..467ba307d0 100644
--- a/src/components/views/auth/ServerConfig.js
+++ b/src/components/views/auth/ServerConfig.js
@@ -210,7 +210,7 @@ export default class ServerConfig extends React.PureComponent {
                         <Field id="mx_ServerConfig_isUrl"
                             label={_t("Identity Server URL")}
                             placeholder={this.props.serverConfig.isUrl}
-                            value={this.state.isUrl}
+                            value={this.state.isUrl || ''}
                             onBlur={this.onIdentityServerBlur}
                             onChange={this.onIdentityServerChange}
                             disabled={this.state.busy}
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index 9ad20bf56c..b2f42afe9e 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -1388,6 +1388,7 @@
     "Change": "Change",
     "Sign in with": "Sign in with",
     "If you don't specify an email address, you won't be able to reset your password. Are you sure?": "If you don't specify an email address, you won't be able to reset your password. Are you sure?",
+    "No Identity Server is configured so you cannot add add an email address in order to reset your password in the future.": "No Identity Server is configured so you cannot add add an email address in order to reset your password in the future.",
     "Use an email address to recover your account": "Use an email address to recover your account",
     "Enter email address (required on this homeserver)": "Enter email address (required on this homeserver)",
     "Doesn't look like a valid email address": "Doesn't look like a valid email address",
@@ -1409,6 +1410,7 @@
     "Create your Matrix account on <underlinedServerName />": "Create your Matrix account on <underlinedServerName />",
     "Use an email address to recover your account.": "Use an email address to recover your account.",
     "Other users can invite you to rooms using your contact details.": "Other users can invite you to rooms using your contact details.",
+    "No Identity Server is configured: no email addreses can be added. You will be unable to reset your password.": "No Identity Server is configured: no email addreses can be added. You will be unable to reset your password.",
     "Other servers": "Other servers",
     "Enter custom server URLs <a>What does this mean?</a>": "Enter custom server URLs <a>What does this mean?</a>",
     "Homeserver URL": "Homeserver URL",
diff --git a/src/utils/AutoDiscoveryUtils.js b/src/utils/AutoDiscoveryUtils.js
index c21377a034..e94c454a3e 100644
--- a/src/utils/AutoDiscoveryUtils.js
+++ b/src/utils/AutoDiscoveryUtils.js
@@ -18,6 +18,7 @@ import React from 'react';
 import {AutoDiscovery} from "matrix-js-sdk";
 import {_t, _td, newTranslatableError} from "../languageHandler";
 import {makeType} from "./TypeUtils";
+import SdkConfig from '../SdkConfig';
 
 const LIVELINESS_DISCOVERY_ERRORS = [
     AutoDiscovery.ERROR_INVALID_HOMESERVER,
@@ -133,11 +134,14 @@ export default class AutoDiscoveryUtils {
             "m.homeserver": {
                 base_url: homeserverUrl,
             },
-            "m.identity_server": {
-                base_url: identityUrl,
-            },
         };
 
+        if (identityUrl) {
+            wellknownConfig['m.identity_server'] = {
+                base_url: identityUrl,
+            };
+        }
+
         const result = await AutoDiscovery.fromDiscoveryConfig(wellknownConfig);
 
         const url = new URL(homeserverUrl);
@@ -179,14 +183,16 @@ export default class AutoDiscoveryUtils {
         const hsResult = discoveryResult['m.homeserver'];
         const isResult = discoveryResult['m.identity_server'];
 
+        const defaultConfig = SdkConfig.get()["validated_server_config"];
+
         // Validate the identity server first because an invalid identity server causes
         // and invalid homeserver, which may not be picked up correctly.
 
-        // Note: In the cases where we rely on this pre-populated "https://vector.im" (namely
+        // Note: In the cases where we rely on the default IS from the config (namely
         // lack of identity server provided by the discovery method), we intentionally do not
-        // validate it. We already know the IS is an IS, and this helps some off-the-grid usage
+        // validate it. This has already been validated and this helps some off-the-grid usage
         // of Riot.
-        let preferredIdentityUrl = "https://vector.im";
+        let preferredIdentityUrl = defaultConfig && defaultConfig['isUrl'];
         if (isResult && isResult.state === AutoDiscovery.SUCCESS) {
             preferredIdentityUrl = isResult["base_url"];
         } else if (isResult && isResult.state !== AutoDiscovery.PROMPT) {