diff --git a/.drone.yml b/.drone.yml
index 5243887..4d9dd2d 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -12,7 +12,7 @@ steps:
     environment:
       COMPOSER_CACHE_DIR: /tmp/cache
     commands:
-      - composer install --no-progress --no-interaction
+      - composer install --no-progress --no-interaction --ignore-platform-reqs
 
   - name: run unit tests
     image: php:7.4
diff --git a/.env.develop b/.env.develop
index 968fd4b..f6a431d 100644
--- a/.env.develop
+++ b/.env.develop
@@ -3,21 +3,23 @@
 # composer: Set cache directory
 COMPOSER_CACHE_DIR=./.composer
 
-# MariaDB container
+# Environment variables for MariaDB container
 MYSQL_RANDOM_ROOT_PASSWORD=yes
 MYSQL_DATABASE=mailusers
 MYSQL_USER=mailaccountadmin
 MYSQL_PASSWORD=mailaccountadmin
 
 # App settings
+APP_TITLE="MailAccountAdmin [dev]"
+APP_ENV=development
 APP_DEBUG=true
+APP_TIMEZONE=Europe/Berlin
 
-# - Disable Twig cache
+# Disable Twig cache
 TWIG_CACHE_DIR=
-TWIG_STRICT=true
 
-# - Database credentials
+# Database credentials
 DB_HOST=db
 DB_DATABASE=mailusers
-DB_USER=mailaccountadmin
+DB_USERNAME=mailaccountadmin
 DB_PASSWORD=mailaccountadmin
diff --git a/.gitignore b/.gitignore
index 646c542..37cecc0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,5 +10,9 @@
 # PHP
 /.composer
 /.phpunit.cache
+/.twig.cache
 /coverage
 /vendor
+
+# Production settings
+/config/app.yml
diff --git a/Dockerfile b/Dockerfile
index 695e69b..89effb8 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,8 +3,10 @@ FROM php:7.4-apache AS base
 WORKDIR /var/www
 
 RUN apt-get update && \
-    apt-get install -y libzip-dev unzip git && \
-    docker-php-ext-install pdo pdo_mysql zip
+    apt-get install -y git unzip libyaml-dev libzip-dev && \
+    docker-php-ext-install pdo pdo_mysql zip && \
+    pecl install yaml && \
+    docker-php-ext-enable yaml
 
 RUN a2enmod rewrite && \
     sed -ri -e 's!/var/www/html!/var/www/public!g' /etc/apache2/sites-available/*.conf
@@ -18,8 +20,6 @@ RUN cp $PHP_INI_DIR/php.ini-development $PHP_INI_DIR/php.ini && \
     pecl install xdebug && \
     docker-php-ext-enable xdebug
 
-ENV APP_ENV=development
-
 # TODO: production image untested
 #FROM base AS production
 #
diff --git a/Makefile b/Makefile
index f0ffbb1..8f22fbd 100644
--- a/Makefile
+++ b/Makefile
@@ -9,7 +9,7 @@ DOCKER_RUN = $(DOCKER_COMPOSE) run --rm app
 COMPOSER = $(DOCKER_RUN) composer
 PHPUNIT = $(DOCKER_RUN) vendor/bin/phpunit
 
-.PHONY: all clean VERSION \
+.PHONY: all clean version \
 	docker-up docker-up-detached docker-down docker-restart docker-build docker-rebuild docker-purge docker-logs docker-run \
 	composer-install composer-install-no-dev composer-update composer-cmd \
 	test phpunit open-coverage
@@ -99,7 +99,7 @@ open-coverage:
 
 # Create VERSION file from current git tag
 version:
-	git describe | tee VERSION
+	git describe --tags | tee VERSION
 
 
 # Clean up
diff --git a/TODO.md b/TODO.md
index 2226cf1..4697f74 100644
--- a/TODO.md
+++ b/TODO.md
@@ -4,7 +4,6 @@
 
 ## General
 
-- Settings from a config file
 - Database migrations
 - Documentation
     - App deployment
@@ -12,6 +11,7 @@
 - Refactor auth and session handling
 
 ## Admin user management
+
 - Create/edit/delete admins
 - Change own password
 
diff --git a/composer.json b/composer.json
index 93dcd53..aa59362 100644
--- a/composer.json
+++ b/composer.json
@@ -14,6 +14,7 @@
     "require": {
         "php": "^7.4",
         "ext-pdo": "*",
+        "ext-yaml": "*",
         "slim/slim": "^4.8",
         "slim/psr7": "^1.3",
         "php-di/php-di": "^6.3",
diff --git a/config/app.develop.yml b/config/app.develop.yml
new file mode 100644
index 0000000..923ceb4
--- /dev/null
+++ b/config/app.develop.yml
@@ -0,0 +1,19 @@
+# Config file for local development (same settings as .env.develop)
+
+# -- App settings
+appTitle: "MailAccountAdmin [dev]"
+environment: development
+debug: true
+timezone: Europe/Berlin
+
+# -- Twig settings
+twig:
+  cacheDir:
+
+# -- Database settings
+database:
+  host: db
+  port: 3306
+  name: mailusers
+  username: mailaccountadmin
+  password: mailaccountadmin
diff --git a/config/app.example.yml b/config/app.example.yml
new file mode 100644
index 0000000..2683c29
--- /dev/null
+++ b/config/app.example.yml
@@ -0,0 +1,23 @@
+# This is an example config file for MailAccountAdmin.
+# Copy this file to /config/app.yml and change as needed.
+# Settings that are commented out represent the default values.
+
+# -- App settings
+# appTitle: MailAccountAdmin
+# environment: production
+# debug: false
+# timezone: UTC
+# dateTimeFormat: r
+
+# -- Twig settings
+twig:
+  # Cache directory for Twig templates (default: unset, which means no cache is used)
+  cacheDir: .twig.cache
+
+# -- Database settings
+database:
+  host: localhost
+  port: 3306
+  name: mailusers
+  username: mailaccountadmin
+  password: very_secret_password
diff --git a/public/index.php b/public/index.php
index 37641db..c918330 100644
--- a/public/index.php
+++ b/public/index.php
@@ -3,19 +3,25 @@ declare(strict_types=1);
 
 require_once __DIR__ . '/../vendor/autoload.php';
 
+use MailAccountAdmin\Config\Loaders\AutoConfigLoader;
 use MailAccountAdmin\Dependencies;
 use MailAccountAdmin\Middlewares;
 use MailAccountAdmin\Routes;
-use MailAccountAdmin\Settings;
 use Slim\Factory\AppFactory;
 
+const ROOT_DIR = __DIR__ . '/..';
+
 session_start();
 
-$settings = new Settings();
-$container = Dependencies::createContainer($settings);
+// Load application config (from config file or environment variables)
+$configLoader = new AutoConfigLoader();
+$config = $configLoader->loadConfig();
+
+// Create application
+$container = Dependencies::createContainer($config);
 $app = AppFactory::createFromContainer($container);
 
-Middlewares::setMiddlewares($app, $settings);
+Middlewares::setMiddlewares($app, $config);
 Routes::setRoutes($app);
 
 $app->run();
diff --git a/public/static/style.css b/public/static/style.css
index 3806bf2..02f1dbc 100644
--- a/public/static/style.css
+++ b/public/static/style.css
@@ -27,6 +27,10 @@ a:hover, a:focus {
     text-decoration: underline;
 }
 
+.monospace {
+    font-family: monospace;
+}
+
 .gray {
     color: gray;
 }
@@ -248,7 +252,6 @@ details > summary {
 
 details > p {
     margin: 0.75rem 1rem;
-    font-family: monospace;
 }
 
 /* -- Detail columns -- */
diff --git a/sql/init_tables.sql b/sql/init_tables.sql
index 0383dd8..ca50ffa 100644
--- a/sql/init_tables.sql
+++ b/sql/init_tables.sql
@@ -35,11 +35,12 @@ CREATE TABLE `mail_users`
 
 CREATE TABLE `mail_aliases`
 (
-    `alias_id`     int(10) unsigned NOT NULL AUTO_INCREMENT,
-    `user_id`      int(10) unsigned NOT NULL,
-    `mail_address` varchar(255)     NOT NULL,
-    `created_at`   datetime         NOT NULL DEFAULT NOW(),
-    `modified_at`  datetime         NOT NULL DEFAULT NOW(),
+    `alias_id`          int(10) unsigned NOT NULL AUTO_INCREMENT,
+    `user_id`           int(10) unsigned NOT NULL,
+    `mail_address`      varchar(255)     NOT NULL,
+    `wildcard_priority` smallint(6)      NOT NULL DEFAULT 0,
+    `created_at`        datetime         NOT NULL DEFAULT NOW(),
+    `modified_at`       datetime         NOT NULL DEFAULT NOW(),
     PRIMARY KEY (`alias_id`),
     UNIQUE KEY `mail_address` (`mail_address`),
     KEY `user_id` (`user_id`),
diff --git a/src/Common/FormData.php b/src/Common/FormData.php
index fde1281..8041257 100644
--- a/src/Common/FormData.php
+++ b/src/Common/FormData.php
@@ -20,7 +20,7 @@ abstract class FormData
             throw new InputValidationError("$fieldName is required.");
         } elseif (strlen($raw) < $minLength) {
             throw new InputValidationError("$fieldName is too short (minimum $minLength characters).");
-        } elseif (strlen($raw) > 100) {
+        } elseif (strlen($raw) > $maxLength) {
             throw new InputValidationError("$fieldName is too long (maximum $maxLength characters).");
         }
         return $raw;
@@ -44,25 +44,42 @@ abstract class FormData
 
     // Input validation - Application specific validators
 
-    protected static function validateUsername(string $username, bool $required = true, string $fieldName = 'Username'): ?string
+    private static function validateMailAddress(string $address, bool $required = true, string $fieldName = 'Mail address'): ?string
     {
-        if (!$required && $username === '') {
+        // Note: This validator allows '%' as wildcard character inside mail addresses.
+        if (!$required && $address === '') {
             return null;
         }
 
-        $username = strtolower(
-            self::validateString($username, 3, 100, $fieldName)
+        $address = strtolower(
+            self::validateString($address, 3, 100, $fieldName)
         );
 
-        if (!preg_match('/^[a-z0-9._+-]+@[a-z0-9.-]+$/', $username) || preg_match('/^\\.|\\.\\.|\\.@|@\\.|\\.$/', $username)) {
+        if (!preg_match('/^[a-z0-9%._+-]+@[a-z0-9%.-]+$/', $address) || preg_match('/^\\.|\\.\\.|\\.@|@\\.|\\.$/', $address)) {
             throw new InputValidationError("$fieldName is not valid (must be a valid mail address).");
         }
+        return $address;
+    }
+
+    protected static function validateUsername(string $username, bool $required = true): ?string
+    {
+        $username = self::validateMailAddress($username, $required, 'Username');
+
+        if ($username !== null && strpos($username, '%') !== false) {
+            throw new InputValidationError('Username must not contain the wildcard character "%" (use a wildcard alias instead).');
+        }
         return $username;
     }
 
-    protected static function validateAliasAddress(string $aliasAddress): string
+    protected static function validateAliasAddress(string $aliasAddress, bool $isWildcard): string
     {
-        return self::validateUsername($aliasAddress, true, 'Alias address');
+        $aliasAddress = self::validateMailAddress($aliasAddress, true, 'Alias address');
+
+        // Check if the address contains a wildcard character
+        if (!$isWildcard && strpos($aliasAddress, '%') !== false) {
+            throw new InputValidationError('Non-wildcard alias address must not contain "%" character.');
+        }
+        return $aliasAddress;
     }
 
     protected static function validatePassword(string $password, string $passwordRepeat, bool $required = true): ?string
diff --git a/src/Config/AppConfig.php b/src/Config/AppConfig.php
new file mode 100644
index 0000000..ce94e39
--- /dev/null
+++ b/src/Config/AppConfig.php
@@ -0,0 +1,105 @@
+<?php
+declare(strict_types=1);
+
+namespace MailAccountAdmin\Config;
+
+class AppConfig
+{
+    // App settings
+    protected string $appTitle = 'MailAccountAdmin';
+    protected string $environment = 'production';
+    protected bool $debug = false;
+    protected string $timezone;
+    protected string $dateTimeFormat = 'r';
+
+    // Twig settings
+    protected ?string $twigCacheDir = null;
+
+    // Database settings
+    protected string $databaseHost = 'localhost';
+    protected int $databasePort = 3306;
+    protected string $databaseName = '';
+    protected string $databaseUsername = '';
+    protected string $databasePassword = '';
+
+    protected function __construct()
+    {
+        // Set default timezone from php.ini
+        $this->timezone = ini_get('date.timezone') ?: 'UTC';
+    }
+
+    public static function createFromArray(array $configArray): self
+    {
+        $config = new self();
+
+        foreach ($configArray as $key => $value) {
+            assert(property_exists($config, $key));
+
+            if ($value !== null) {
+                $config->$key = $value;
+            }
+        }
+
+        return $config;
+    }
+
+    public function getAppTitle(): string
+    {
+        return $this->appTitle;
+    }
+
+    public function getAppEnvironment(): string
+    {
+        return $this->environment;
+    }
+
+    public function isDebugMode(): bool
+    {
+        return $this->debug;
+    }
+
+    public function getTimezone(): string
+    {
+        return $this->timezone;
+    }
+
+    public function getDateTimeFormat(): string
+    {
+        // Specify datetime format (https://www.php.net/manual/en/datetime.format.php)
+        // Default value "r": RFC 2822 formatted date (Thu, 21 Dec 2000 16:01:07 +0200)
+        return $this->dateTimeFormat;
+    }
+
+    public function getTwigCacheDir(): ?string
+    {
+        if (empty($this->twigCacheDir)) {
+            return null;
+        } elseif (substr($this->twigCacheDir, 0, 1) === '/') {
+            // Absolute path
+            return $this->twigCacheDir;
+        } else {
+            // Relative path
+            return ROOT_DIR . '/' . $this->twigCacheDir;
+        }
+    }
+
+    public function getTwigSettings(): array
+    {
+        return [
+            'cache' => $this->getTwigCacheDir() ?: false,
+            'debug' => $this->isDebugMode(),
+            'strict_variables' => $this->isDebugMode(),
+        ];
+    }
+
+    public function getDatabaseSettings(): array
+    {
+        return [
+            'host' => $this->databaseHost,
+            'port' => $this->databasePort,
+            'dbname' => $this->databaseName,
+            'username' => $this->databaseUsername,
+            'password' => $this->databasePassword,
+        ];
+    }
+}
diff --git a/src/Config/Loaders/AutoConfigLoader.php b/src/Config/Loaders/AutoConfigLoader.php
new file mode 100644
index 0000000..6ba336c
--- /dev/null
+++ b/src/Config/Loaders/AutoConfigLoader.php
@@ -0,0 +1,28 @@
+<?php
+declare(strict_types=1);
+
+namespace MailAccountAdmin\Config\Loaders;
+
+use MailAccountAdmin\Config\AppConfig;
+
+class AutoConfigLoader implements ConfigLoaderInterface
+{
+    private ConfigLoaderInterface $configLoader;
+
+    public function __construct()
+    {
+        $yamlFilePath = ROOT_DIR . '/config/app.yml';
+
+        // Check if yml config file exists
+        if (file_exists($yamlFilePath)) {
+            $this->configLoader = new YamlConfigLoader($yamlFilePath);
+        } else {
+            $this->configLoader = new EnvConfigLoader();
+        }
+    }
+
+    public function loadConfig(): AppConfig
+    {
+        return $this->configLoader->loadConfig();
+    }
+}
diff --git a/src/Config/Loaders/ConfigLoaderInterface.php b/src/Config/Loaders/ConfigLoaderInterface.php
new file mode 100644
index 0000000..ed8ebe6
--- /dev/null
+++ b/src/Config/Loaders/ConfigLoaderInterface.php
@@ -0,0 +1,11 @@
+<?php
+declare(strict_types=1);
+
+namespace MailAccountAdmin\Config\Loaders;
+
+use MailAccountAdmin\Config\AppConfig;
+
+interface ConfigLoaderInterface
+{
+    public function loadConfig(): AppConfig;
+}
diff --git a/src/Config/Loaders/EnvConfigLoader.php b/src/Config/Loaders/EnvConfigLoader.php
new file mode 100644
index 0000000..3dc8f29
--- /dev/null
+++ b/src/Config/Loaders/EnvConfigLoader.php
@@ -0,0 +1,31 @@
+<?php
+declare(strict_types=1);
+
+namespace MailAccountAdmin\Config\Loaders;
+
+use MailAccountAdmin\Config\AppConfig;
+
+class EnvConfigLoader implements ConfigLoaderInterface
+{
+    public function loadConfig(): AppConfig
+    {
+        return AppConfig::createFromArray([
+            // App settings
+            'appTitle' => getenv('APP_TITLE') ?: null,
+            'environment' => getenv('APP_ENV') ?: null,
+            'debug' => getenv('APP_DEBUG') === 'true' ? true : null,
+            'timezone' => getenv('APP_TIMEZONE') ?: null,
+            'dateTimeFormat' => getenv('APP_DATE_TIME_FORMAT') ?: null,
+
+            // Twig settings
+            'twigCacheDir' => getenv('TWIG_CACHE_DIR') ?: null,
+
+            // Database settings
+            'databaseHost' => getenv('DB_HOST') ?: null,
+            'databasePort' => (int)getenv('DB_PORT') ?: null,
+            'databaseName' => getenv('DB_DATABASE') ?: null,
+            'databaseUsername' => getenv('DB_USERNAME') ?: null,
+            'databasePassword' => getenv('DB_PASSWORD') ?: null,
+        ]);
+    }
+}
diff --git a/src/Config/Loaders/YamlConfigLoader.php b/src/Config/Loaders/YamlConfigLoader.php
new file mode 100644
index 0000000..61b5cb1
--- /dev/null
+++ b/src/Config/Loaders/YamlConfigLoader.php
@@ -0,0 +1,48 @@
+<?php
+declare(strict_types=1);
+
+namespace MailAccountAdmin\Config\Loaders;
+
+use MailAccountAdmin\Config\AppConfig;
+
+class YamlConfigLoader implements ConfigLoaderInterface
+{
+    private string $filePath;
+
+    public function __construct(string $filePath)
+    {
+        assert(file_exists($filePath));
+
+        $this->filePath = $filePath;
+    }
+
+    public function loadConfig(): AppConfig
+    {
+        // Parse yml config file
+        $parsedConfig = yaml_parse_file($this->filePath);
+
+        // Check datatypes
+        assert(is_array($parsedConfig));
+        assert(!isset($parsedConfig['twig']) || is_array($parsedConfig['twig']));
+        assert(!isset($parsedConfig['database']) || is_array($parsedConfig['database']));
+
+        return AppConfig::createFromArray([
+            // App settings
+            'appTitle' => $parsedConfig['appTitle'] ?? null,
+            'environment' => $parsedConfig['environment'] ?? null,
+            'debug' => isset($parsedConfig['debug']) ? (bool)$parsedConfig['debug'] : null,
+            'timezone' => $parsedConfig['timezone'] ?? null,
+            'dateTimeFormat' => $parsedConfig['dateTimeFormat'] ?? null,
+
+            // Twig settings
+            'twigCacheDir' => $parsedConfig['twig']['cacheDir'] ?? null,
+
+            // Database settings
+            'databaseHost' => $parsedConfig['database']['host'] ?? null,
+            'databasePort' => isset($parsedConfig['database']['port']) ? (int)$parsedConfig['database']['port'] : null,
+            'databaseName' => $parsedConfig['database']['name'] ?? null,
+            'databaseUsername' => $parsedConfig['database']['username'] ?? null,
+            'databasePassword' => $parsedConfig['database']['password'] ?? null,
+        ]);
+    }
+}
diff --git a/src/Dependencies.php b/src/Dependencies.php
index 94c0d64..30dd467 100644
--- a/src/Dependencies.php
+++ b/src/Dependencies.php
@@ -7,6 +7,7 @@ use DI\Container;
 use MailAccountAdmin\Common\PasswordHelper;
 use MailAccountAdmin\Common\SessionHelper;
 use MailAccountAdmin\Common\UserHelper;
+use MailAccountAdmin\Config\AppConfig;
 use MailAccountAdmin\Frontend\Accounts\AccountController;
 use MailAccountAdmin\Frontend\Accounts\AccountHandler;
 use MailAccountAdmin\Frontend\Domains\DomainController;
@@ -23,43 +24,43 @@ use Twig\Extension\CoreExtension as TwigCoreExtension;
 
 class Dependencies
 {
-    public const SETTINGS = 'settings';
+    public const CONFIG = 'config';
     public const TWIG = 'view';
     private const TWIG_TEMPLATE_DIR = __DIR__ . '/../templates';
     public const DATABASE = 'database';
 
-    public static function createContainer(Settings $settings): Container
+    public static function createContainer(AppConfig $config): Container
     {
         $container = new Container();
 
-        // App settings
-        $container->set(self::SETTINGS, $settings);
+        // App configuration
+        $container->set(self::CONFIG, $config);
 
         // App information
         $container->set(AppInfo::class, function (ContainerInterface $c) {
-            /** @var Settings $settings */
-            $settings = $c->get(self::SETTINGS);
-            $versionHelper = new VersionHelper();
+            /** @var AppConfig $config */
+            $config = $c->get(self::CONFIG);
+            $versionHelper = new VersionHelper($config);
 
             return new AppInfo(
-                $settings->getAppTitle(),
+                $config->getAppTitle(),
                 $versionHelper->getAppVersion(),
             );
         });
 
         // Twig template engine
         $container->set(self::TWIG, function (ContainerInterface $c) {
-            /** @var Settings $settings */
-            $settings = $c->get(self::SETTINGS);
+            /** @var AppConfig $config */
+            $config = $c->get(self::CONFIG);
 
             // Create Twig view
-            $twig = Twig::create(self::TWIG_TEMPLATE_DIR, $settings->getTwigSettings());
+            $twig = Twig::create(self::TWIG_TEMPLATE_DIR, $config->getTwigSettings());
 
             // Set default date format
             /** @var TwigCoreExtension $coreExtension */
             $coreExtension = $twig->getEnvironment()->getExtension(TwigCoreExtension::class);
-            $coreExtension->setDateFormat($settings->getDateFormat());
-            $coreExtension->setTimezone($settings->getTimezone());
+            $coreExtension->setDateFormat($config->getDateTimeFormat());
+            $coreExtension->setTimezone($config->getTimezone());
 
             // Add app information to globals
             $appInfo = $c->get(AppInfo::class);
@@ -71,9 +72,9 @@ class Dependencies
 
         // Database connection
         $container->set(self::DATABASE, function (ContainerInterface $c) {
-            /** @var Settings $settings */
-            $settings = $c->get(self::SETTINGS);
-            $dbSettings = $settings->getDatabaseSettings();
+            /** @var AppConfig $config */
+            $config = $c->get(self::CONFIG);
+            $dbSettings = $config->getDatabaseSettings();
 
             return new PDO(
                 "mysql:dbname={$dbSettings['dbname']};host={$dbSettings['host']};port={$dbSettings['port']}",
@@ -108,7 +109,7 @@ class Dependencies
         });
 
         // Helper classes
-        $container->set(SessionHelper::class, function (ContainerInterface $c) {
+        $container->set(SessionHelper::class, function () {
             return new SessionHelper();
         });
 
@@ -120,7 +121,7 @@ class Dependencies
             );
         });
 
-        $container->set(PasswordHelper::class, function (ContainerInterface $c) {
+        $container->set(PasswordHelper::class, function () {
             return new PasswordHelper();
         });
 
diff --git a/src/Frontend/Accounts/AccountAddAliasData.php b/src/Frontend/Accounts/AccountAddAliasData.php
index 6e5a3c6..4a2469e 100644
--- a/src/Frontend/Accounts/AccountAddAliasData.php
+++ b/src/Frontend/Accounts/AccountAddAliasData.php
@@ -4,20 +4,34 @@ declare(strict_types=1);
 namespace MailAccountAdmin\Frontend\Accounts;
 
 use MailAccountAdmin\Common\FormData;
+use MailAccountAdmin\Exceptions\InputValidationError;
 
 class AccountAddAliasData extends FormData
 {
     private string $aliasAddress;
+    private bool $isWildcard;
+    private int $wildcardPriority;
 
-    private function __construct(string $aliasAddress)
+    private function __construct(string $aliasAddress, bool $isWildcard, int $wildcardPriority)
     {
+        if ($isWildcard && $wildcardPriority === 0) {
+            throw new InputValidationError('Wildcard alias must have a wildcard priority other than 0.');
+        } elseif (!$isWildcard) {
+            $wildcardPriority = 0;
+        }
+
         $this->aliasAddress = $aliasAddress;
+        $this->isWildcard = $isWildcard;
+        $this->wildcardPriority = $wildcardPriority;
     }
 
     public static function createFromArray(array $raw): self
     {
+        $isWildcard = self::validateBoolOption(trim($raw['is_wildcard'] ?? ''));
         return new self(
-            self::validateAliasAddress(trim($raw['alias_address'] ?? '')),
+            self::validateAliasAddress(trim($raw['alias_address'] ?? ''), $isWildcard),
+            $isWildcard,
+            self::validateInteger(trim($raw['wildcard_priority'] ?? '')),
         );
     }
 
@@ -25,4 +39,14 @@ class AccountAddAliasData extends FormData
     {
         return $this->aliasAddress;
     }
+
+    public function isWildcard(): bool
+    {
+        return $this->isWildcard;
+    }
+
+    public function getWildcardPriority(): int
+    {
+        return $this->wildcardPriority;
+    }
 }
diff --git a/src/Frontend/Accounts/AccountHandler.php b/src/Frontend/Accounts/AccountHandler.php
index 4a71fc0..b9a0650 100644
--- a/src/Frontend/Accounts/AccountHandler.php
+++ b/src/Frontend/Accounts/AccountHandler.php
@@ -278,14 +278,22 @@ class AccountHandler
         // Check if account exists
         $this->ensureAccountExists($accountId);
 
+        $unescapedAddress = $address = $aliasAddData->getAliasAddress();
+        $wildcardPriority = 0;
+
+        if ($aliasAddData->isWildcard()) {
+            // If it's a wildcard alias, escape underscores
+            $address = str_replace('_', '\\_', $address);
+            $wildcardPriority = $aliasAddData->getWildcardPriority();
+        }
+
         // Check if alias address is still available
-        $address = $aliasAddData->getAliasAddress();
         if (!$this->accountRepository->checkUsernameAvailable($address) || !$this->aliasRepository->checkAliasAvailable($address)) {
-            throw new InputValidationError("Alias address \"$address\" is not available.");
+            throw new InputValidationError("Alias address \"$unescapedAddress\" is not available.");
         }
 
         // Create alias in database
-        $this->aliasRepository->createNewAlias($accountId, $address);
+        $this->aliasRepository->createNewAlias($accountId, $address, $wildcardPriority);
     }
 
 
diff --git a/src/Middlewares.php b/src/Middlewares.php
index 375e481..f60987f 100644
--- a/src/Middlewares.php
+++ b/src/Middlewares.php
@@ -4,14 +4,15 @@ declare(strict_types=1);
 namespace MailAccountAdmin;
 
 use MailAccountAdmin\Auth\AuthMiddleware;
+use MailAccountAdmin\Config\AppConfig;
 use Slim\App;
 use Slim\Views\TwigMiddleware;
 
 class Middlewares
 {
-    public static function setMiddlewares(App $app, Settings $settings): void
+    public static function setMiddlewares(App $app, AppConfig $config): void
     {
-        $displayErrorDetails = $settings->isDebugMode();
+        $displayErrorDetails = $config->isDebugMode();
 
         $app->addErrorMiddleware($displayErrorDetails, true, true);
         $app->add(new AuthMiddleware());
diff --git a/src/Models/Alias.php b/src/Models/Alias.php
index 3fe7413..e636c82 100644
--- a/src/Models/Alias.php
+++ b/src/Models/Alias.php
@@ -10,14 +10,23 @@ class Alias
     private int $id;
     private int $userId;
     private string $mailAddress;
+    private int $wildcardPriority;
     private DateTimeImmutable $createdAt;
     private DateTimeImmutable $modifiedAt;
 
-    private function __construct(int $id, int $userId, string $mailAddress, DateTimeImmutable $createdAt, DateTimeImmutable $modifiedAt)
+    private function __construct(
+        int $id,
+        int $userId,
+        string $mailAddress,
+        int $wildcardPriority,
+        DateTimeImmutable $createdAt,
+        DateTimeImmutable $modifiedAt
+    )
     {
         $this->id = $id;
         $this->userId = $userId;
         $this->mailAddress = $mailAddress;
+        $this->wildcardPriority = $wildcardPriority;
         $this->createdAt = $createdAt;
         $this->modifiedAt = $modifiedAt;
     }
@@ -28,6 +37,7 @@ class Alias
             (int)$data['alias_id'],
             (int)$data['user_id'],
             $data['mail_address'],
+            (int)$data['wildcard_priority'],
             new DateTimeImmutable($data['created_at']),
             new DateTimeImmutable($data['modified_at']),
         );
@@ -43,11 +53,24 @@ class Alias
         return $this->userId;
     }
 
-    public function getMailAddress(): string
+    public function getMailAddress(bool $unescape = true): string
     {
+        if ($this->isWildcard() && $unescape) {
+            return str_replace('\\_', '_', $this->mailAddress);
+        }
         return $this->mailAddress;
     }
 
+    public function isWildcard(): bool
+    {
+        return $this->wildcardPriority !== 0;
+    }
+
+    public function getWildcardPriority(): int
+    {
+        return $this->wildcardPriority;
+    }
+
     public function getCreatedAt(): DateTimeImmutable
     {
         return $this->createdAt;
diff --git a/src/Repositories/AliasRepository.php b/src/Repositories/AliasRepository.php
index 45ed640..9a4d615 100644
--- a/src/Repositories/AliasRepository.php
+++ b/src/Repositories/AliasRepository.php
@@ -11,11 +11,11 @@ class AliasRepository extends BaseRepository
 {
     public function fetchAliasesForUserId(int $userId): array
     {
-        $statement = $this->pdo->prepare('SELECT * FROM mail_aliases WHERE user_id = :user_id ORDER BY mail_address');
+        $statement = $this->pdo->prepare('SELECT * FROM mail_aliases WHERE user_id = :user_id ORDER BY wildcard_priority, mail_address');
         $statement->execute(['user_id' => $userId]);
         $rows = $statement->fetchAll(PDO::FETCH_ASSOC);
 
-        // Create Account models from rows
+        // Create Alias models from rows
         $aliasList = [];
         foreach ($rows as $row) {
             $aliasList[] = Alias::createFromArray($row);
@@ -43,12 +43,20 @@ class AliasRepository extends BaseRepository
         return $statement->rowCount() === 0;
     }
 
-    public function createNewAlias(int $userId, string $mailAddress): void
+    public function createNewAlias(int $userId, string $mailAddress, int $wildcardPriority = 0): void
     {
-        $statement = $this->pdo->prepare('INSERT INTO mail_aliases (user_id, mail_address) VALUES (:user_id, :mail_address)');
+        $query = '
+            INSERT INTO mail_aliases
+            (user_id, mail_address, wildcard_priority)
+            VALUES
+            (:user_id, :mail_address, :wildcard_priority)
+        ';
+
+        $statement = $this->pdo->prepare($query);
         $statement->execute([
             'user_id' => $userId,
             'mail_address' => $mailAddress,
+            'wildcard_priority' => $wildcardPriority,
         ]);
     }
 
diff --git a/src/Settings.php b/src/Settings.php
deleted file mode 100644
index 4d1b989..0000000
--- a/src/Settings.php
+++ /dev/null
@@ -1,49 +0,0 @@
-<?php
-declare(strict_types=1);
-
-namespace MailAccountAdmin;
-
-class Settings
-{
-    public function getAppTitle(): string
-    {
-        return getenv('APP_TITLE') ?: 'MailAccountAdmin';
-    }
-
-    public function isDebugMode(): bool
-    {
-        return getenv('APP_DEBUG') === 'true';
-    }
-
-    public function getTimezone(): string
-    {
-        return 'Europe/Berlin';
-    }
-
-    public function getDateFormat(): string
-    {
-        // Default date format (https://www.php.net/manual/en/datetime.format.php)
-        // RFC 2822 formatted date (Thu, 21 Dec 2000 16:01:07 +0200)
-        return 'r';
-    }
-
-    public function getTwigSettings(): array
-    {
-        return [
-            'cache' => getenv('TWIG_CACHE_DIR') ?: false,
-            'debug' => $this->isDebugMode(),
-            'strict_variables' => getenv('TWIG_STRICT') === 'true',
-        ];
-    }
-
-    public function getDatabaseSettings(): array
-    {
-        return [
-            'host' => getenv('DB_HOST') ?: 'localhost',
-            'port' => getenv('DB_PORT') ?: 3306,
-            'dbname' => getenv('DB_DATABASE') ?: '',
-            'username' => getenv('DB_USER') ?: '',
-            'password' => getenv('DB_PASSWORD') ?: '',
-        ];
-    }
-}
diff --git a/src/VersionHelper.php b/src/VersionHelper.php
index 4fd370a..1223bce 100644
--- a/src/VersionHelper.php
+++ b/src/VersionHelper.php
@@ -3,16 +3,18 @@ declare(strict_types=1);
 
 namespace MailAccountAdmin;
 
+use MailAccountAdmin\Config\AppConfig;
+
 class VersionHelper
 {
     private string $version;
 
-    public function __construct()
+    public function __construct(AppConfig $config)
     {
         $version = $this->loadFromVersionFile();
         if (!empty($version)) {
             $this->version = $version;
-        } elseif ($this->inDevelopmentMode()) {
+        } elseif ($config->getAppEnvironment() === 'development') {
             $this->version = '[dev version]';
         } else {
             $this->version = '[undefined version]';
@@ -34,9 +36,4 @@ class VersionHelper
         }
         return null;
     }
-
-    private function inDevelopmentMode(): bool
-    {
-        return getenv('APP_ENV') === 'development';
-    }
 }
diff --git a/templates/account_create.html.twig b/templates/account_create.html.twig
index 246aae7..15c8bd2 100644
--- a/templates/account_create.html.twig
+++ b/templates/account_create.html.twig
@@ -24,7 +24,7 @@
             </p>
             <details>
                 <summary>Show list of known domains</summary>
-                <p>{{ domainList ? domainList | join(', ') : 'No domains exist yet.' }}</p>
+                <p class="monospace">{{ domainList ? domainList | join(', ') : 'No domains exist yet.' }}</p>
             </details>
             <table>
                 <tr>
diff --git a/templates/account_details.html.twig b/templates/account_details.html.twig
index 0c092cc..3ef481d 100644
--- a/templates/account_details.html.twig
+++ b/templates/account_details.html.twig
@@ -71,13 +71,21 @@
             <table class="bordered_table">
                 <tr>
                     <th></th>
-                    <th>Address</th>
+                    <th style="min-width: 16em">Address</th>
+                    <th>Wildcard (priority)</th>
                     <th>Created at</th>
                 </tr>
                 {% for alias in aliases %}
                     <tr>
                         <td><input type="checkbox" id="delete_selected_{{ alias.getId() }}" name="selected_aliases[]" value="{{ alias.getId() }}"/></td>
                         <td><label for="delete_selected_{{ alias.getId() }}">{{ alias.getMailAddress() }}</label></td>
+                        <td>
+                            {% if alias.isWildcard() %}
+                                Yes ({{ alias.getWildcardPriority() }})
+                            {% else %}
+                                <span class="gray">No</span>
+                            {% endif %}
+                        </td>
                         <td>{{ alias.getCreatedAt() | date }}</td>
                     </tr>
                 {% endfor %}
@@ -95,7 +103,18 @@
             <tr>
                 <td><label for="add_alias_address">New alias:</label></td>
                 <td>
-                    <input id="add_alias_address" name="alias_address" value="{{ formData['new_alias'] | default('') }}" {{ success is defined or error is defined ? 'autofocus': '' }}/>
+                    <input id="add_alias_address" name="alias_address" value="{{ formData['alias_address'] | default('') }}" {{ success is defined or error is defined ? 'autofocus': '' }}/>
+                </td>
+            </tr>
+            <tr>
+                <td style="vertical-align: top">Wildcard:</td>
+                <td style="vertical-align: top">
+                    <label>
+                        <input type="checkbox" name="is_wildcard" {{ formData is defined and formData['is_wildcard'] | default() ? 'checked' : '' }}/>
+                        Create wildcard alias,
+                    </label>
+                    <label for="add_alias_wildcard_priority">priority:</label>
+                    <input type="number" id="add_alias_wildcard_priority" name="wildcard_priority" value="{{ formData['wildcard_priority'] | default('1') }}" style="width: 6em"/>
                 </td>
             </tr>
             <tr>
@@ -104,5 +123,18 @@
                 </td>
             </tr>
         </table>
+
+        <details>
+            <summary>How to define wildcard aliases?</summary>
+            <p>
+                Wildcard aliases use <code>%</code> as a placeholder for any amount of characters (zero or more),
+                e.g. <code>%@example.com</code> or <code>example-%@example.com</code>.
+            </p>
+            <p>
+                Additionally, a <b>wildcard priority</b> must be specified. When a mail address is looked up that
+                matches multiple (wildcard) aliases, the alias with the <b>lowest</b> wildcard priority will be used.
+                The priority must not be 0 (internally, the value 0 stands for regular non-wildcard aliases).
+            </p>
+        </details>
     </form>
 {% endblock %}
diff --git a/templates/base.html.twig b/templates/base.html.twig
index c364b6d..bd0d091 100644
--- a/templates/base.html.twig
+++ b/templates/base.html.twig
@@ -12,7 +12,11 @@
 <header>
     <h1>{{ app_info.getTitle() }}</h1>
     <div class="header_appversion">
-        <a href="{{ app_info.getRepositoryUrl() }}">{{ app_info.getVersion() }}</a>
+        {% if logged_in | default() %}
+            <a href="{{ app_info.getRepositoryUrl() }}">{{ app_info.getVersion() }}</a>
+        {% else %}
+            {{ app_info.getVersion() }}
+        {% endif %}
     </div>
     <div class="header_spacer"></div>
     <div class="header_userstatus">