diff --git a/phpBB/docs/install-config.sample.yml b/phpBB/docs/install-config.sample.yml
index a354e52e2f..5ef6c643be 100644
--- a/phpBB/docs/install-config.sample.yml
+++ b/phpBB/docs/install-config.sample.yml
@@ -23,7 +23,6 @@ installer:
         smtp_delivery : ~
         smtp_host: ~
         smtp_port: ~
-        smtp_auth: ~
         smtp_user: ~
         smtp_pass: ~
 
diff --git a/phpBB/includes/acp/acp_board.php b/phpBB/includes/acp/acp_board.php
index bda5661278..2afa79b1e6 100644
--- a/phpBB/includes/acp/acp_board.php
+++ b/phpBB/includes/acp/acp_board.php
@@ -473,7 +473,6 @@ class acp_board
 						'smtp_delivery'			=> array('lang' => 'USE_SMTP',				'validate' => 'bool',	'type' => 'radio:yes_no', 'explain' => true),
 						'smtp_host'				=> array('lang' => 'SMTP_SERVER',			'validate' => 'string',	'type' => 'text:25:50', 'explain' => true),
 						'smtp_port'				=> array('lang' => 'SMTP_PORT',				'validate' => 'int:0:99999',	'type' => 'number:0:99999', 'explain' => true),
-						'smtp_auth_method'		=> array('lang' => 'SMTP_AUTH_METHOD',		'validate' => 'string',	'type' => 'select', 'method' => 'mail_auth_select', 'explain' => true),
 						'smtp_username'			=> array('lang' => 'SMTP_USERNAME',			'validate' => 'string',	'type' => 'text:25:255', 'explain' => true),
 						'smtp_password'			=> array('lang' => 'SMTP_PASSWORD',			'validate' => 'string',	'type' => 'password:25:255', 'explain' => true),
 						'smtp_verify_peer'		=> array('lang' => 'SMTP_VERIFY_PEER',		'validate' => 'bool',	'type' => 'radio:yes_no', 'explain' => true),
@@ -884,30 +883,6 @@ class acp_board
 		];
 	}
 
-	/**
-	* Select mail authentication method
-	*/
-	function mail_auth_select($selected_method, $key = '')
-	{
-		global $user;
-
-		$auth_methods = ['PLAIN', 'LOGIN', 'CRAM-MD5', 'DIGEST-MD5', 'POP-BEFORE-SMTP'];
-		$s_smtp_auth_options = [];
-
-		foreach ($auth_methods as $method)
-		{
-			$s_smtp_auth_options[] = [
-				'value'		=> $method,
-				'selected'	=> $selected_method == $method,
-				'label'		=> $user->lang('SMTP_' . str_replace('-', '_', $method)),
-			];
-		}
-
-		return [
-			'options' => $s_smtp_auth_options,
-		];
-	}
-
 	/**
 	* Select full folder action
 	*/
diff --git a/phpBB/includes/questionnaire/questionnaire.php b/phpBB/includes/questionnaire/questionnaire.php
index 74675e0e03..319537f3e3 100644
--- a/phpBB/includes/questionnaire/questionnaire.php
+++ b/phpBB/includes/questionnaire/questionnaire.php
@@ -435,7 +435,6 @@ class phpbb_questionnaire_phpbb_data_provider
 			'secure_downloads' => true,
 			'session_gc' => true,
 			'session_length' => true,
-			'smtp_auth_method' => true,
 			'smtp_delivery' => true,
 			'topics_per_page' => true,
 			'version' => true,
diff --git a/phpBB/install/schemas/schema_data.sql b/phpBB/install/schemas/schema_data.sql
index 21b26ee9c8..43b8f95fc8 100644
--- a/phpBB/install/schemas/schema_data.sql
+++ b/phpBB/install/schemas/schema_data.sql
@@ -287,7 +287,6 @@ INSERT INTO phpbb_config (config_name, config_value) VALUES ('sitename_short', '
 INSERT INTO phpbb_config (config_name, config_value) VALUES ('smilies_path', 'images/smilies');
 INSERT INTO phpbb_config (config_name, config_value) VALUES ('smilies_per_page', '50');
 INSERT INTO phpbb_config (config_name, config_value) VALUES ('smtp_allow_self_signed', '0');
-INSERT INTO phpbb_config (config_name, config_value) VALUES ('smtp_auth_method', 'PLAIN');
 INSERT INTO phpbb_config (config_name, config_value) VALUES ('smtp_delivery', '0');
 INSERT INTO phpbb_config (config_name, config_value) VALUES ('smtp_host', '');
 INSERT INTO phpbb_config (config_name, config_value) VALUES ('smtp_port', '25');
diff --git a/phpBB/language/en/acp/board.php b/phpBB/language/en/acp/board.php
index 633df91138..e46091c954 100644
--- a/phpBB/language/en/acp/board.php
+++ b/phpBB/language/en/acp/board.php
@@ -553,15 +553,8 @@ $lang = array_merge($lang, array(
 	'SEND_TEST_EMAIL_EXPLAIN'		=> 'This will send a test email to the address defined in your account.',
 	'SMTP_ALLOW_SELF_SIGNED'		=> 'Allow self-signed SSL certificates',
 	'SMTP_ALLOW_SELF_SIGNED_EXPLAIN'=> 'Allow connections to SMTP server with self-signed SSL certificate. <br><em><strong>Warning:</strong> Allowing self-signed SSL certificates may cause security implications.</em>',
-	'SMTP_AUTH_METHOD'				=> 'Authentication method for SMTP',
-	'SMTP_AUTH_METHOD_EXPLAIN'		=> 'Only used if a username/password is set, ask your provider if you are unsure which method to use.',
-	'SMTP_CRAM_MD5'					=> 'CRAM-MD5',
-	'SMTP_DIGEST_MD5'				=> 'DIGEST-MD5',
-	'SMTP_LOGIN'					=> 'LOGIN',
 	'SMTP_PASSWORD'					=> 'SMTP password',
 	'SMTP_PASSWORD_EXPLAIN'			=> 'Only enter a password if your SMTP server requires it.<br><em><strong>Warning:</strong> This password will be stored as plain text in the database, visible to everybody who can access your database or who can view this configuration page.</em>',
-	'SMTP_PLAIN'					=> 'PLAIN',
-	'SMTP_POP_BEFORE_SMTP'			=> 'POP-BEFORE-SMTP',
 	'SMTP_PORT'						=> 'SMTP server port',
 	'SMTP_PORT_EXPLAIN'				=> 'Only change this if you know your SMTP server is on a different port.',
 	'SMTP_SERVER'					=> 'SMTP server address',
diff --git a/phpBB/phpbb/db/migration/data/v400/remove_smtp_auth_method.php b/phpBB/phpbb/db/migration/data/v400/remove_smtp_auth_method.php
new file mode 100644
index 0000000000..eed17067b7
--- /dev/null
+++ b/phpBB/phpbb/db/migration/data/v400/remove_smtp_auth_method.php
@@ -0,0 +1,38 @@
+<?php
+/**
+*
+* This file is part of the phpBB Forum Software package.
+*
+* @copyright (c) phpBB Limited <https://www.phpbb.com>
+* @license GNU General Public License, version 2 (GPL-2.0)
+*
+* For full copyright and license information, please see
+* the docs/CREDITS.txt file.
+*
+*/
+
+namespace phpbb\db\migration\data\v400;
+
+use phpbb\db\migration\migration;
+
+class remove_smtp_auth_method extends migration
+{
+	public function effectively_installed()
+	{
+		return !$this->config->offsetExists('smtp_auth_method');
+	}
+
+	public static function depends_on()
+	{
+		return [
+			'\phpbb\db\migration\data\v400\dev',
+		];
+	}
+
+	public function update_data()
+	{
+		return [
+			['config.remove', ['smtp_auth_method']],
+		];
+	}
+}
diff --git a/phpBB/phpbb/install/console/command/install/install.php b/phpBB/phpbb/install/console/command/install/install.php
index 84c8aa688a..6641f9b944 100644
--- a/phpBB/phpbb/install/console/command/install/install.php
+++ b/phpBB/phpbb/install/console/command/install/install.php
@@ -195,7 +195,6 @@ class install extends \phpbb\console\command\command
 		$iohandler->set_input('smtp_delivery', $config['email']['smtp_delivery']);
 		$iohandler->set_input('smtp_host', $config['email']['smtp_host']);
 		$iohandler->set_input('smtp_port', $config['email']['smtp_port']);
-		$iohandler->set_input('smtp_auth', $config['email']['smtp_auth']);
 		$iohandler->set_input('smtp_user', $config['email']['smtp_user']);
 		$iohandler->set_input('smtp_pass', $config['email']['smtp_pass']);
 		$iohandler->set_input('submit_email', 'submit');
diff --git a/phpBB/phpbb/install/installer_configuration.php b/phpBB/phpbb/install/installer_configuration.php
index 974080dc55..f1051095e2 100644
--- a/phpBB/phpbb/install/installer_configuration.php
+++ b/phpBB/phpbb/install/installer_configuration.php
@@ -97,9 +97,6 @@ class installer_configuration implements ConfigurationInterface
 						->scalarNode('smtp_port')
 							->defaultValue(null)
 							->end()
-						->scalarNode('smtp_auth')
-							->defaultValue(null)
-							->end()
 						->scalarNode('smtp_user')
 							->defaultValue(null)
 							->end()
diff --git a/phpBB/phpbb/install/module/install_database/task/add_config_settings.php b/phpBB/phpbb/install/module/install_database/task/add_config_settings.php
index 5b9a9da536..14c88a04d3 100644
--- a/phpBB/phpbb/install/module/install_database/task/add_config_settings.php
+++ b/phpBB/phpbb/install/module/install_database/task/add_config_settings.php
@@ -150,7 +150,6 @@ class add_config_settings extends database_task
 			'smtp_delivery'		=> $this->install_config->get('smtp_delivery'),
 			'smtp_host'			=> $this->install_config->get('smtp_host'),
 			'smtp_port'			=> $this->install_config->get('smtp_port'),
-			'smtp_auth_method'	=> $this->install_config->get('smtp_auth'),
 			'smtp_username'		=> $this->install_config->get('smtp_user'),
 			'smtp_password'		=> $this->install_config->get('smtp_pass'),
 
diff --git a/phpBB/phpbb/install/module/obtain_data/task/obtain_email_data.php b/phpBB/phpbb/install/module/obtain_data/task/obtain_email_data.php
index 93c0eb385e..3c6508f6a7 100644
--- a/phpBB/phpbb/install/module/obtain_data/task/obtain_email_data.php
+++ b/phpBB/phpbb/install/module/obtain_data/task/obtain_email_data.php
@@ -52,12 +52,9 @@ class obtain_email_data extends \phpbb\install\task_base implements \phpbb\insta
 		$smtp_delivery	= $this->io_handler->get_input('smtp_delivery', '');
 		$smtp_host		= $this->io_handler->get_input('smtp_host', '', true);
 		$smtp_port		= $this->io_handler->get_input('smtp_port', '');
-		$smtp_auth		= $this->io_handler->get_input('smtp_auth', '');
 		$smtp_user		= $this->io_handler->get_input('smtp_user', '', true);
 		$smtp_passwd	= $this->io_handler->get_input('smtp_pass', '', true);
 
-		$auth_methods = array('PLAIN', 'LOGIN', 'CRAM-MD5', 'DIGEST-MD5', 'POP-BEFORE-SMTP');
-
 		// Check if data is sent
 		if ($this->io_handler->get_input('submit_email', false))
 		{
@@ -65,22 +62,11 @@ class obtain_email_data extends \phpbb\install\task_base implements \phpbb\insta
 			$this->install_config->set('smtp_delivery', $smtp_delivery);
 			$this->install_config->set('smtp_host', $smtp_host);
 			$this->install_config->set('smtp_port', $smtp_port);
-			$this->install_config->set('smtp_auth', $smtp_auth);
 			$this->install_config->set('smtp_user', $smtp_user);
 			$this->install_config->set('smtp_pass', $smtp_passwd);
 		}
 		else
 		{
-			$auth_options = array();
-			foreach ($auth_methods as $method)
-			{
-				$auth_options[] = array(
-					'value'		=> $method,
-					'label'		=> 'SMTP_' . str_replace('-', '_', $method),
-					'selected'	=> false,
-				);
-			}
-
 			$email_form = array(
 				'email_enable' => array(
 					'label'			=> 'ENABLE_EMAIL',
@@ -126,12 +112,6 @@ class obtain_email_data extends \phpbb\install\task_base implements \phpbb\insta
 					'type'			=> 'text',
 					'default'		=> $smtp_port,
 				),
-				'smtp_auth' => array(
-					'label'			=> 'SMTP_AUTH_METHOD',
-					'description'	=> 'SMTP_AUTH_METHOD_EXPLAIN',
-					'type'			=> 'select',
-					'options'		=> $auth_options,
-				),
 				'smtp_user' => array(
 					'label'			=> 'SMTP_USERNAME',
 					'description'	=> 'SMTP_USERNAME_EXPLAIN',
diff --git a/tests/test_framework/phpbb_functional_test_case.php b/tests/test_framework/phpbb_functional_test_case.php
index ddfca1e0be..3e9b654b0e 100644
--- a/tests/test_framework/phpbb_functional_test_case.php
+++ b/tests/test_framework/phpbb_functional_test_case.php
@@ -419,7 +419,6 @@ class phpbb_functional_test_case extends phpbb_test_case
 		$iohandler->set_input('email_enable', true);
 		$iohandler->set_input('smtp_delivery', '1');
 		$iohandler->set_input('smtp_host', '');
-		$iohandler->set_input('smtp_auth', 'PLAIN');
 		$iohandler->set_input('smtp_user', 'nxuser');
 		$iohandler->set_input('smtp_pass', 'nxpass');
 		$iohandler->set_input('submit_email', 'submit');
diff --git a/vagrant/phpbb-install-config.yml b/vagrant/phpbb-install-config.yml
index db7b525b9f..0b89958299 100644
--- a/vagrant/phpbb-install-config.yml
+++ b/vagrant/phpbb-install-config.yml
@@ -38,7 +38,6 @@ installer:
         enabled: false
         smtp_delivery : ~
         smtp_host: ~
-        smtp_auth: ~
         smtp_user: ~
         smtp_pass: ~