diff --git a/app/Controllers/NotificationGroupController.php b/app/Controllers/NotificationGroupController.php
index 067979d..a171174 100644
--- a/app/Controllers/NotificationGroupController.php
+++ b/app/Controllers/NotificationGroupController.php
@@ -463,7 +463,9 @@ class NotificationGroupController extends Controller
             'email' => 'Email',
             'telegram' => 'Telegram',
             'discord' => 'Discord',
-            'slack' => 'Slack'
+            'slack' => 'Slack',
+            'mattermost' => 'Mattermost',
+            'webhook' => 'Webhook'
         ];
 
         $channelName = $channelNames[$channelType] ?? ucfirst($channelType);
@@ -532,6 +534,17 @@ class NotificationGroupController extends Controller
                 }
                 return ['webhook_url' => $webhookUrl];
 
+            case 'mattermost':
+                $webhookUrl = trim($data['mattermost_webhook_url'] ?? '');
+                if (empty($webhookUrl) || !filter_var($webhookUrl, FILTER_VALIDATE_URL)) {
+                    return null;
+                }
+                // Validate Mattermost webhook URL format
+                if (!str_contains($webhookUrl, '/hooks/')) {
+                    return null;
+                }
+                return ['webhook_url' => $webhookUrl];
+
             case 'webhook':
                 $webhookUrl = trim($data['webhook_url'] ?? '');
                 if (empty($webhookUrl) || !filter_var($webhookUrl, FILTER_VALIDATE_URL)) {
diff --git a/app/Services/Channels/MattermostChannel.php b/app/Services/Channels/MattermostChannel.php
new file mode 100644
index 0000000..ba66734
--- /dev/null
+++ b/app/Services/Channels/MattermostChannel.php
@@ -0,0 +1,107 @@
+<?php
+
+namespace App\Services\Channels;
+
+use GuzzleHttp\Client;
+use App\Services\Logger;
+
+class MattermostChannel implements NotificationChannelInterface
+{
+    private Client $client;
+    private Logger $logger;
+
+    public function __construct()
+    {
+        $this->client = new Client(['timeout' => 10]);
+        $this->logger = new Logger('mattermost_channel');
+    }
+
+    public function send(array $config, string $message, array $data = []): bool
+    {
+        if (!isset($config['webhook_url'])) {
+            return false;
+        }
+
+        try {
+            // Mattermost expects a simple text payload or attachments
+            $payload = [
+                'text' => $message
+            ];
+
+            // Add attachments for richer formatting if domain data is available
+            if (isset($data['domain'])) {
+                $color = $this->getColorByDaysLeft($data['days_left'] ?? null);
+                
+                $payload['attachments'] = [
+                    [
+                        'color' => $color,
+                        'title' => '🔔 Domain Expiration Alert',
+                        'text' => $message,
+                        'fields' => [
+                            [
+                                'short' => true,
+                                'title' => 'Domain',
+                                'value' => $data['domain']
+                            ],
+                            [
+                                'short' => true,
+                                'title' => 'Days Left',
+                                'value' => $data['days_left'] ?? 'N/A'
+                            ],
+                            [
+                                'short' => true,
+                                'title' => 'Expiration Date',
+                                'value' => $data['expiration_date'] ?? 'N/A'
+                            ],
+                            [
+                                'short' => true,
+                                'title' => 'Registrar',
+                                'value' => $data['registrar'] ?? 'N/A'
+                            ]
+                        ],
+                        'footer' => 'Domain Monitor',
+                        'ts' => time()
+                    ]
+                ];
+            }
+
+            $response = $this->client->post($config['webhook_url'], [
+                'json' => $payload
+            ]);
+
+            $ok = $response->getStatusCode() === 200;
+            if ($ok) {
+                $this->logger->info('Mattermost message sent', [
+                    'status' => $response->getStatusCode()
+                ]);
+            } else {
+                $this->logger->error('Mattermost non-200 status', [
+                    'status' => $response->getStatusCode()
+                ]);
+            }
+            return $ok;
+        } catch (\Exception $e) {
+            $this->logger->error('Mattermost send failed', [
+                'exception' => $e->getMessage()
+            ]);
+            return false;
+        }
+    }
+
+    private function getColorByDaysLeft(?int $daysLeft): string
+    {
+        if ($daysLeft === null) {
+            return '#36a64f'; // Green
+        }
+
+        if ($daysLeft <= 0) {
+            return '#ff0000'; // Red - expired
+        } elseif ($daysLeft <= 1) {
+            return '#ff6600'; // Orange - critical
+        } elseif ($daysLeft <= 7) {
+            return '#ffaa00'; // Yellow - warning
+        } else {
+            return '#36a64f'; // Green - ok
+        }
+    }
+}
diff --git a/app/Services/NotificationService.php b/app/Services/NotificationService.php
index f518224..066e589 100644
--- a/app/Services/NotificationService.php
+++ b/app/Services/NotificationService.php
@@ -6,6 +6,7 @@ use App\Services\Channels\EmailChannel;
 use App\Services\Channels\TelegramChannel;
 use App\Services\Channels\DiscordChannel;
 use App\Services\Channels\SlackChannel;
+use App\Services\Channels\MattermostChannel;
 use App\Services\Channels\WebhookChannel;
 
 class NotificationService
@@ -19,6 +20,7 @@ class NotificationService
             'telegram' => new TelegramChannel(),
             'discord' => new DiscordChannel(),
             'slack' => new SlackChannel(),
+            'mattermost' => new MattermostChannel(),
             'webhook' => new WebhookChannel(),
         ];
     }
diff --git a/app/Views/groups/edit.php b/app/Views/groups/edit.php
index 3e89c20..f0c7497 100644
--- a/app/Views/groups/edit.php
+++ b/app/Views/groups/edit.php
@@ -77,9 +77,9 @@ ob_start();
                 <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4 mb-6">
                     <?php foreach ($group['channels'] as $channel): 
                         $config = json_decode($channel['channel_config'], true);
-                        $icons = ['email' => 'fa-envelope', 'telegram' => 'fa-telegram', 'discord' => 'fa-discord', 'slack' => 'fa-slack', 'webhook' => 'fa-link'];
-                        $iconClasses = ['email' => 'fas', 'telegram' => 'fab', 'discord' => 'fab', 'slack' => 'fab', 'webhook' => 'fas'];
-                        $colors = ['email' => 'blue', 'telegram' => 'blue', 'discord' => 'indigo', 'slack' => 'teal', 'webhook' => 'purple'];
+                        $icons = ['email' => 'fa-envelope', 'telegram' => 'fa-telegram', 'discord' => 'fa-discord', 'slack' => 'fa-slack', 'mattermost' => 'fa-comments', 'webhook' => 'fa-link'];
+                        $iconClasses = ['email' => 'fas', 'telegram' => 'fab', 'discord' => 'fab', 'slack' => 'fab', 'mattermost' => 'fab', 'webhook' => 'fas'];
+                        $colors = ['email' => 'blue', 'telegram' => 'blue', 'discord' => 'indigo', 'slack' => 'teal', 'mattermost' => 'green', 'webhook' => 'purple'];
                         $icon = $icons[$channel['channel_type']] ?? 'fa-bell';
                         $iconClass = $iconClasses[$channel['channel_type']] ?? 'fas';
                         $color = $colors[$channel['channel_type']] ?? 'gray';
@@ -157,6 +157,7 @@ ob_start();
                             <option value="telegram">Telegram</option>
                             <option value="discord">Discord</option>
                             <option value="slack">Slack</option>
+                            <option value="mattermost">Mattermost</option>
                             <option value="webhook">Webhook (Custom)</option>
                         </select>
                     </div>
@@ -242,6 +243,24 @@ ob_start();
                         </div>
                     </div>
 
+                    <!-- Mattermost Fields -->
+                    <div id="mattermost_fields" class="hidden space-y-4">
+                        <div>
+                            <label for="mattermost_webhook" class="block text-sm font-medium text-gray-700 mb-1.5">
+                                Webhook URL
+                            </label>
+                            <input type="text" 
+                                   id="mattermost_webhook" 
+                                   name="mattermost_webhook_url" 
+                                   class="w-full px-3 py-2.5 border border-gray-300 rounded-lg focus:ring-2 focus:ring-primary focus:border-primary transition-colors text-sm font-mono" 
+                                   placeholder="https://your-mattermost.com/hooks/..."
+                                   autocomplete="off">
+                            <p class="mt-1.5 text-xs text-gray-500">
+                                Create in Mattermost → Integrations → Incoming Webhooks
+                            </p>
+                        </div>
+                    </div>
+
                     <!-- Generic Webhook Fields -->
                     <div id="webhook_fields" class="hidden space-y-4">
                         <div>
@@ -338,6 +357,7 @@ function toggleChannelFields() {
     const chatIdField = document.getElementById('chat_id');
     const discordWebhook = document.getElementById('discord_webhook');
     const slackWebhook = document.getElementById('slack_webhook');
+    const mattermostWebhook = document.getElementById('mattermost_webhook');
     const genericWebhook = document.getElementById('generic_webhook_url');
     
     // Remove required from all
@@ -346,6 +366,7 @@ function toggleChannelFields() {
     chatIdField.removeAttribute('required');
     discordWebhook.removeAttribute('required');
     slackWebhook.removeAttribute('required');
+    if (mattermostWebhook) mattermostWebhook.removeAttribute('required');
     if (genericWebhook) genericWebhook.removeAttribute('required');
     
     // Hide all fields
@@ -353,6 +374,7 @@ function toggleChannelFields() {
     document.getElementById('telegram_fields').classList.add('hidden');
     document.getElementById('discord_fields').classList.add('hidden');
     document.getElementById('slack_fields').classList.add('hidden');
+    document.getElementById('mattermost_fields').classList.add('hidden');
     document.getElementById('webhook_fields').classList.add('hidden');
     
     // Hide test button by default
@@ -379,6 +401,12 @@ function toggleChannelFields() {
                 slackWebhook.setAttribute('required', 'required');
                 slackWebhook.focus();
                 break;
+            case 'mattermost':
+                if (mattermostWebhook) {
+                    mattermostWebhook.setAttribute('required', 'required');
+                    mattermostWebhook.focus();
+                }
+                break;
             case 'webhook':
                 if (genericWebhook) {
                     genericWebhook.setAttribute('required', 'required');
@@ -434,6 +462,17 @@ if (addChannelForm) {
         }
     }
 
+    // Validate Mattermost webhook
+    if (channelType === 'mattermost') {
+        const webhookUrl = document.getElementById('mattermost_webhook').value.trim();
+        if (!webhookUrl) {
+            e.preventDefault();
+            alert('Please enter the Mattermost webhook URL');
+            document.getElementById('mattermost_webhook').focus();
+            return false;
+        }
+    }
+
     // Validate Generic webhook
     if (channelType === 'webhook') {
         const webhookUrl = document.getElementById('generic_webhook_url').value.trim();
@@ -517,6 +556,13 @@ function testChannel(channelType, existingConfig = null) {
                     errorMessage = 'Please enter a Slack webhook URL';
                 }
                 break;
+            case 'mattermost':
+                const mattermostWebhook = document.getElementById('mattermost_webhook').value.trim();
+                if (!mattermostWebhook) {
+                    isValid = false;
+                    errorMessage = 'Please enter a Mattermost webhook URL';
+                }
+                break;
             case 'webhook':
                 const genericWebhook = document.getElementById('generic_webhook_url').value.trim();
                 if (!genericWebhook) {
@@ -570,6 +616,9 @@ function testChannel(channelType, existingConfig = null) {
             case 'slack':
                 formData.append('slack_webhook_url', existingConfig.webhook_url);
                 break;
+            case 'mattermost':
+                formData.append('mattermost_webhook_url', existingConfig.webhook_url);
+                break;
             case 'webhook':
                 formData.append('webhook_url', existingConfig.webhook_url);
                 break;
@@ -590,6 +639,9 @@ function testChannel(channelType, existingConfig = null) {
             case 'slack':
                 formData.append('slack_webhook_url', document.getElementById('slack_webhook').value);
                 break;
+            case 'mattermost':
+                formData.append('mattermost_webhook_url', document.getElementById('mattermost_webhook').value);
+                break;
             case 'webhook':
                 formData.append('webhook_url', document.getElementById('generic_webhook_url').value);
                 break;
diff --git a/database/migrations/000_initial_schema_v1.1.0.sql b/database/migrations/000_initial_schema_v1.1.0.sql
index 1fa5573..418ad92 100644
--- a/database/migrations/000_initial_schema_v1.1.0.sql
+++ b/database/migrations/000_initial_schema_v1.1.0.sql
@@ -182,7 +182,7 @@ CREATE TABLE IF NOT EXISTS user_notifications (
 CREATE TABLE IF NOT EXISTS notification_channels (
     id INT AUTO_INCREMENT PRIMARY KEY,
     notification_group_id INT NOT NULL,
-    channel_type ENUM('email', 'telegram', 'discord', 'slack', 'webhook') NOT NULL,
+    channel_type ENUM('email', 'telegram', 'discord', 'slack', 'mattermost', 'webhook') NOT NULL,
     channel_config JSON NOT NULL,
     is_active BOOLEAN DEFAULT TRUE,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
diff --git a/database/migrations/019_add_webhook_channel_type.sql b/database/migrations/019_add_webhook_channel_type.sql
index 9482969..10e3cef 100644
--- a/database/migrations/019_add_webhook_channel_type.sql
+++ b/database/migrations/019_add_webhook_channel_type.sql
@@ -1,5 +1,5 @@
--- Add 'webhook' to the channel_type ENUM in notification_channels table
--- This allows custom webhook integrations like Mattermost
+-- Add 'webhook' and 'mattermost' to the channel_type ENUM in notification_channels table
+-- This allows custom webhook integrations and Mattermost support
 
 ALTER TABLE notification_channels 
-MODIFY COLUMN channel_type ENUM('email', 'telegram', 'discord', 'slack', 'webhook') NOT NULL;
+MODIFY COLUMN channel_type ENUM('email', 'telegram', 'discord', 'slack', 'mattermost', 'webhook') NOT NULL;