Mail Config: Updated how TLS is configured

After full review of current MAIL_ENCRYPTION usage in laravel and
smyfony mailer, this updates the options in BookStack to be simplified
and specific in usage:

- Removed mail.mailers.smtp.encryption option since it did not actually
  affect anything in the current state of dependancies.
- Updated MAIL_ENCRYPTION so values of tls OR ssl will force-enable tls
  via 'scheme' option with laravel passes to the SMTP transfport, which
  Smyfony uses as an indicator to force TLS.

When MAIL_ENCRYPTION is not used, STARTTLS will still be attempted by
symfony mailer.
Updated .env files to refer to BookStack docs (which was updated for
this) and to reflect correct default port.
Related to #4342

.env.example

@@ -37,8 +37,10 @@ MAIL_FROM=bookstack@example.com
 # SMTP mail options
 # These settings can be checked using the "Send a Test Email"
 # feature found in the "Settings > Maintenance" area of the system.
+# For more detailed documentation on mail options, refer to:
+# https://www.bookstackapp.com/docs/admin/email-webhooks/#email-configuration
 MAIL_HOST=localhost
-MAIL_PORT=1025
+MAIL_PORT=587
 MAIL_USERNAME=null
 MAIL_PASSWORD=null
 MAIL_ENCRYPTION=null

.env.example.complete

@@ -69,23 +69,19 @@ DB_PASSWORD=database_user_password
 # certificate itself (Common Name or Subject Alternative Name).
 MYSQL_ATTR_SSL_CA="/path/to/ca.pem"
 
-# Mail system to use
+# Mail configuration
-# Can be 'smtp' or 'sendmail'
+# Refer to https://www.bookstackapp.com/docs/admin/email-webhooks/#email-configuration
 MAIL_DRIVER=smtp
-
-# Mail sending options
 MAIL_FROM=mail@bookstackapp.com
 MAIL_FROM_NAME=BookStack
 
-# SMTP mail options
 MAIL_HOST=localhost
-MAIL_PORT=1025
+MAIL_PORT=587
 MAIL_USERNAME=null
 MAIL_PASSWORD=null
 MAIL_ENCRYPTION=null
 MAIL_VERIFY_SSL=true
 
-# Command to use when email is sent via sendmail
 MAIL_SENDMAIL_COMMAND="/usr/sbin/sendmail -bs"
 
 # Cache & Session driver to use

app/Config/mail.php

@@ -8,6 +8,10 @@
  * Do not edit this file unless you're happy to maintain any changes yourself.
  */
 
+// Configured mail encryption method.
+// STARTTLS should still be attempted, but tls/ssl forces TLS usage.
+$mailEncryption = env('MAIL_ENCRYPTION', null);
+
 return [
 
     // Mail driver to use.
@@ -27,9 +31,9 @@ return [
     'mailers' => [
         'smtp' => [
             'transport' => 'smtp',
+            'scheme' => ($mailEncryption === 'tls' || $mailEncryption === 'ssl') ? 'smtps' : null,
             'host' => env('MAIL_HOST', 'smtp.mailgun.org'),
             'port' => env('MAIL_PORT', 587),
-            'encryption' => env('MAIL_ENCRYPTION', 'tls'),
             'username' => env('MAIL_USERNAME'),
             'password' => env('MAIL_PASSWORD'),
             'verify_peer' => env('MAIL_VERIFY_SSL', true),

tests/Unit/ConfigTest.php

@@ -5,6 +5,7 @@ namespace Tests\Unit;
 use Illuminate\Support\Facades\Log;
 use Illuminate\Support\Facades\Mail;
 use Symfony\Component\Mailer\Transport\Smtp\EsmtpTransport;
+use Symfony\Component\Mailer\Transport\Smtp\Stream\SocketStream;
 use Tests\TestCase;
 
 /**
@@ -122,6 +123,45 @@ class ConfigTest extends TestCase
         });
     }
 
+    public function test_non_null_mail_encryption_options_enforce_smtp_scheme()
+    {
+        $this->checkEnvConfigResult('MAIL_ENCRYPTION', 'tls', 'mail.mailers.smtp.scheme', 'smtps');
+        $this->checkEnvConfigResult('MAIL_ENCRYPTION', 'ssl', 'mail.mailers.smtp.scheme', 'smtps');
+        $this->checkEnvConfigResult('MAIL_ENCRYPTION', 'null', 'mail.mailers.smtp.scheme', null);
+    }
+
+    public function test_smtp_scheme_and_certain_port_forces_tls_usage()
+    {
+        $isMailTlsForcedEnabled = function () {
+            $transport = Mail::mailer('smtp')->getSymfonyTransport();
+            /** @var SocketStream $stream */
+            $stream = $transport->getStream();
+            Mail::purge('smtp');
+            return $stream->isTLS();
+        };
+
+        config()->set([
+            'mail.mailers.smtp.scheme' => null,
+            'mail.mailers.smtp.port' => 587,
+        ]);
+
+        $this->assertFalse($isMailTlsForcedEnabled());
+
+        config()->set([
+            'mail.mailers.smtp.scheme' => 'smtps',
+            'mail.mailers.smtp.port' => 587,
+        ]);
+
+        $this->assertTrue($isMailTlsForcedEnabled());
+
+        config()->set([
+            'mail.mailers.smtp.scheme' => '',
+            'mail.mailers.smtp.port' => 465,
+        ]);
+
+        $this->assertTrue($isMailTlsForcedEnabled());
+    }
+
     /**
      * Set an environment variable of the given name and value
      * then check the given config key to see if it matches the given result.