diff --git a/framework/core/js/src/admin/components/MailPage.js b/framework/core/js/src/admin/components/MailPage.js
index 6a7b41e62..dcbbb8f13 100644
--- a/framework/core/js/src/admin/components/MailPage.js
+++ b/framework/core/js/src/admin/components/MailPage.js
@@ -15,6 +15,7 @@ export default class MailPage extends Page {
 
     this.driverFields = {};
     this.fields = ['mail_driver', 'mail_from'];
+    this.fieldsRequired = [];
     this.values = {};
 
     const settings = app.data.settings;
@@ -36,6 +37,8 @@ export default class MailPage extends Page {
         }
       }
 
+      this.fieldsRequired = response['data'].map(driver => driver['attributes']['fieldsRequired']).flat();
+
       this.loading = false;
       m.redraw();
     });
@@ -52,6 +55,8 @@ export default class MailPage extends Page {
       );
     }
 
+    const fields = this.driverFields[this.values.mail_driver()];
+
     return (
       <div className="MailPage">
         <div className="container">
@@ -83,13 +88,18 @@ export default class MailPage extends Page {
               ]
             })}
 
-            {Object.keys(this.driverFields[this.values.mail_driver()]).length > 0 && FieldSet.component({
+            {Object.keys(fields).length > 0 && FieldSet.component({
               label: app.translator.trans(`core.admin.email.${this.values.mail_driver()}_heading`),
               className: 'MailPage-MailSettings',
               children: [
+                fields.filter(field => this.fieldsRequired.includes(field) && !this.values[field]()).length > 0 && Alert.component({
+                  children: app.translator.trans('core.admin.email.incomplete_configuration_text'),
+                  dismissible: false,
+                }),
+
                 <div className="MailPage-MailSettings-input">
-                  {Object.keys(this.driverFields[this.values.mail_driver()]).map(field => [
-                    <label>{app.translator.trans(`core.admin.email.${field}_label`)}</label>,
+                  {Object.keys(fields).map(field => [
+                    <label>{app.translator.trans(`core.admin.email.${field}_label`)} {this.fieldsRequired.includes(field) ? '*' : ''}</label>,
                     this.renderField(field),
                   ])}
                 </div>
@@ -115,7 +125,7 @@ export default class MailPage extends Page {
     const prop = this.values[name];
 
     if (typeof field === 'string') {
-      return <input className="FormControl" value={prop() || ''} oninput={m.withAttr('value', prop)}/>;
+      return <input className="FormControl" value={prop() || ''} oninput={m.withAttr('value', prop)} required={this.fieldsRequired.includes(field)} />;
     } else {
       return <Select value={prop()} options={field} onchange={prop} />;
     }
diff --git a/framework/core/src/Api/Serializer/MailDriverSerializer.php b/framework/core/src/Api/Serializer/MailDriverSerializer.php
index 03a23dcfe..6b0b81824 100644
--- a/framework/core/src/Api/Serializer/MailDriverSerializer.php
+++ b/framework/core/src/Api/Serializer/MailDriverSerializer.php
@@ -47,6 +47,7 @@ class MailDriverSerializer extends AbstractSerializer
 
         return [
             'fields' => $settings,
+            'fieldsRequired' => $driver['driver']->requiredFields(),
         ];
     }
 
diff --git a/framework/core/src/Mail/DriverInterface.php b/framework/core/src/Mail/DriverInterface.php
index d4c2f18e6..c1802d552 100644
--- a/framework/core/src/Mail/DriverInterface.php
+++ b/framework/core/src/Mail/DriverInterface.php
@@ -31,6 +31,11 @@ interface DriverInterface
      */
     public function availableSettings(): array;
 
+    /**
+     * Provide a list of required settings for this driver.
+     */
+    public function requiredFields(): array;
+
     /**
      * Build a mail transport based on Flarum's current settings.
      */
diff --git a/framework/core/src/Mail/LogDriver.php b/framework/core/src/Mail/LogDriver.php
index afa2025b2..137b57951 100644
--- a/framework/core/src/Mail/LogDriver.php
+++ b/framework/core/src/Mail/LogDriver.php
@@ -31,6 +31,11 @@ class LogDriver implements DriverInterface
         return [];
     }
 
+    public function requiredFields(): array
+    {
+        return [];
+    }
+
     public function buildTransport(SettingsRepositoryInterface $settings): Swift_Transport
     {
         return new LogTransport($this->logger);
diff --git a/framework/core/src/Mail/MailServiceProvider.php b/framework/core/src/Mail/MailServiceProvider.php
index c8ca8f0e0..1e492b49c 100644
--- a/framework/core/src/Mail/MailServiceProvider.php
+++ b/framework/core/src/Mail/MailServiceProvider.php
@@ -33,7 +33,15 @@ class MailServiceProvider extends AbstractServiceProvider
             $settings = $this->app->make(SettingsRepositoryInterface::class);
             $drivers = $this->app->make('mail.supported_drivers');
 
-            return $this->app->make($drivers[$settings->get('mail_driver')]);
+            $driver = $this->app->make($drivers[$settings->get('mail_driver')]);
+
+            // check that all required fields have been filled
+            $settings = $this->app->make(SettingsRepositoryInterface::class);
+            $valid = $driver && array_reduce($driver->requiredFields(), function ($carry, $field) use ($settings) {
+                return $carry && ! empty($settings->get($field));
+            }, true);
+
+            return $valid ? $driver : $this->app->make(NullDriver::class);
         });
 
         $this->app->alias('mail.driver', DriverInterface::class);
diff --git a/framework/core/src/Mail/MailgunDriver.php b/framework/core/src/Mail/MailgunDriver.php
index d600db6b4..2b11efcd9 100644
--- a/framework/core/src/Mail/MailgunDriver.php
+++ b/framework/core/src/Mail/MailgunDriver.php
@@ -28,6 +28,11 @@ class MailgunDriver implements DriverInterface
         ];
     }
 
+    public function requiredFields(): array
+    {
+        return $this->availableSettings();
+    }
+
     public function buildTransport(SettingsRepositoryInterface $settings): Swift_Transport
     {
         return new MailgunTransport(
diff --git a/framework/core/src/Mail/MandrillDriver.php b/framework/core/src/Mail/MandrillDriver.php
index 45a0c4051..d45236e60 100644
--- a/framework/core/src/Mail/MandrillDriver.php
+++ b/framework/core/src/Mail/MandrillDriver.php
@@ -23,6 +23,11 @@ class MandrillDriver implements DriverInterface
         ];
     }
 
+    public function requiredFields(): array
+    {
+        return $this->availableSettings();
+    }
+
     public function buildTransport(SettingsRepositoryInterface $settings): Swift_Transport
     {
         return new MandrillTransport(
diff --git a/framework/core/src/Mail/NullDriver.php b/framework/core/src/Mail/NullDriver.php
new file mode 100644
index 000000000..acddd51df
--- /dev/null
+++ b/framework/core/src/Mail/NullDriver.php
@@ -0,0 +1,32 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * For detailed copyright and license information, please view the
+ * LICENSE file that was distributed with this source code.
+ */
+
+namespace Flarum\Mail;
+
+use Flarum\Settings\SettingsRepositoryInterface;
+use Swift_NullTransport;
+use Swift_Transport;
+
+class NullDriver implements DriverInterface
+{
+    public function availableSettings(): array
+    {
+        return [];
+    }
+
+    public function requiredFields(): array
+    {
+        return [];
+    }
+
+    public function buildTransport(SettingsRepositoryInterface $settings): Swift_Transport
+    {
+        return new Swift_NullTransport();
+    }
+}
diff --git a/framework/core/src/Mail/SendmailDriver.php b/framework/core/src/Mail/SendmailDriver.php
index da7213cf9..937d93452 100644
--- a/framework/core/src/Mail/SendmailDriver.php
+++ b/framework/core/src/Mail/SendmailDriver.php
@@ -20,6 +20,11 @@ class SendmailDriver implements DriverInterface
         return [];
     }
 
+    public function requiredFields(): array
+    {
+        return [];
+    }
+
     public function buildTransport(SettingsRepositoryInterface $settings): Swift_Transport
     {
         return new Swift_SendmailTransport;
diff --git a/framework/core/src/Mail/SesDriver.php b/framework/core/src/Mail/SesDriver.php
index 8248bab0e..89f1cd61f 100644
--- a/framework/core/src/Mail/SesDriver.php
+++ b/framework/core/src/Mail/SesDriver.php
@@ -25,6 +25,11 @@ class SesDriver implements DriverInterface
         ];
     }
 
+    public function requiredFields(): array
+    {
+        return $this->availableSettings();
+    }
+
     public function buildTransport(SettingsRepositoryInterface $settings): Swift_Transport
     {
         $config = [
diff --git a/framework/core/src/Mail/SmtpDriver.php b/framework/core/src/Mail/SmtpDriver.php
index b6233cfe8..6818a3565 100644
--- a/framework/core/src/Mail/SmtpDriver.php
+++ b/framework/core/src/Mail/SmtpDriver.php
@@ -21,8 +21,17 @@ class SmtpDriver implements DriverInterface
             'mail_host' => '', // a hostname, IPv4 address or IPv6 wrapped in []
             'mail_port' => '', // a number, defaults to 25
             'mail_encryption' => '', // "tls" or "ssl"
-            'mail_username' => '', // required
-            'mail_password' => '', // required
+            'mail_username' => '',
+            'mail_password' => '',
+        ];
+    }
+
+    public function requiredFields(): array
+    {
+        return [
+            'mail_host',
+            'mail_username',
+            'mail_password',
         ];
     }