diff --git a/htdocs/admin/mails.php b/htdocs/admin/mails.php
index 9145ad9a1a7..0504315075d 100644
--- a/htdocs/admin/mails.php
+++ b/htdocs/admin/mails.php
@@ -292,7 +292,7 @@ if ($action == 'edit') {
                             jQuery("#smtp_port_mess").hide();
 							jQuery(".smtp_method").show();
                             jQuery(".dkim").show();
-							jQuery(".smtp_auth_method").hide();
+							jQuery(".smtp_auth_method").show();
                         }
                     }
 					function change_smtp_auth_method() {
@@ -300,6 +300,9 @@ if ($action == 'edit') {
 						if (jQuery("#MAIN_MAIL_SENDMODE").val()==\'smtps\' && jQuery("#radio_oauth").prop("checked")) {
 							jQuery(".smtp_oauth_service").show();
 							jQuery(".smtp_pw").hide();
+						} else if (jQuery("#MAIN_MAIL_SENDMODE").val()==\'swiftmailer\' && jQuery("#radio_oauth").prop("checked")) {
+							jQuery(".smtp_oauth_service").show();
+							jQuery(".smtp_pw").hide();
 						} else if(jQuery("#MAIN_MAIL_SENDMODE").val()==\'mail\'){
 							jQuery(".smtp_oauth_service").hide();
 							jQuery(".smtp_pw").hide();
@@ -465,13 +468,13 @@ if ($action == 'edit') {
 	if (!empty($conf->use_javascript_ajax) || (isset($conf->global->MAIN_MAIL_SENDMODE) && in_array($conf->global->MAIN_MAIL_SENDMODE, array('smtps', 'swiftmailer')))) {
 		print '<tr class="oddeven smtp_auth_method"><td>'.$langs->trans("MAIN_MAIL_SMTPS_AUTH_TYPE").'</td><td>';
 		if (empty($conf->multicompany->enabled) || ($user->admin && !$user->entity)) {
-			print '<input type="radio" id="radio_pw" name="MAIN_MAIL_SMTPS_AUTH_TYPE" value="LOGIN"'.($conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE == 'LOGIN' ? ' checked' : '').'> ';
+			print '<input type="radio" id="radio_pw" name="MAIN_MAIL_SMTPS_AUTH_TYPE" value="LOGIN"'.(getDolGlobalString('MAIN_MAIL_SMTPS_AUTH_TYPE') == 'LOGIN' ? ' checked' : '').'> ';
 			print '<label for="radio_pw" >'.$langs->trans("UsePassword").'</label>';
 			print '&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;';
-			print '<input type="radio" id="radio_oauth" name="MAIN_MAIL_SMTPS_AUTH_TYPE" value="XOAUTH2"'.($conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE == 'XOAUTH2' ? ' checked' : '').'> ';
+			print '<input type="radio" id="radio_oauth" name="MAIN_MAIL_SMTPS_AUTH_TYPE" value="XOAUTH2"'.(getDolGlobalString('MAIN_MAIL_SMTPS_AUTH_TYPE') == 'XOAUTH2' ? ' checked' : '').'> ';
 			print '<label for="radio_oauth" >'.$form->textwithpicto($langs->trans("UseOauth"), $langs->trans("OauthNotAvailableForAllAndHadToBeCreatedBefore")).'</label>';
 		} else {
-			$value = $conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE;
+			$value = getDolGlobalString('MAIN_MAIL_SMTPS_AUTH_TYPE', 'LOGIN');
 			$htmltext = $langs->trans("ContactSuperAdminForChange");
 			print $form->textwithpicto($langs->trans("MAIN_MAIL_SMTPS_AUTH_TYPE"), $htmltext, 1, 'superadmin');
 			print '<input type="hidden" id="MAIN_MAIL_SMTPS_AUTH_TYPE" name="MAIN_MAIL_SMTPS_AUTH_TYPE" value="'.$value.'">';
@@ -497,7 +500,7 @@ if ($action == 'edit') {
 	}
 
 	// OAUTH service provider
-	if (!empty($conf->use_javascript_ajax) || (isset($conf->global->MAIN_MAIL_SENDMODE) && in_array($conf->global->MAIN_MAIL_SENDMODE, array('smtps')))) {
+	if (!empty($conf->use_javascript_ajax) || (isset($conf->global->MAIN_MAIL_SENDMODE) && in_array($conf->global->MAIN_MAIL_SENDMODE, array('smtps', 'swiftmailer')))) {
 		print '<tr class="oddeven smtp_oauth_service"><td>'.$langs->trans("MAIN_MAIL_SMTPS_OAUTH_SERVICE").'</td><td>';
 
 		// SuperAdministrator access only
@@ -679,7 +682,7 @@ if ($action == 'edit') {
 		print '</td></tr>';
 
 		// Host server
-		if ($linuxlike && (isset($conf->global->MAIN_MAIL_SENDMODE) && $conf->global->MAIN_MAIL_SENDMODE == 'mail')) {
+		if ($linuxlike && (getDolGlobalString('MAIN_MAIL_SENDMODE') == 'mail')) {
 			print '<tr class="oddeven"><td>'.$langs->trans("MAIN_MAIL_SMTP_SERVER_NotAvailableOnLinuxLike").'</td><td><span class="opacitymedium">'.$langs->trans("SeeLocalSendMailSetup").'</span></td></tr>';
 		} else {
 			print '<tr class="oddeven"><td>'.$langs->trans("MAIN_MAIL_SMTP_SERVER", ini_get('SMTP') ?ini_get('SMTP') : $langs->transnoentities("Undefined")).'</td><td>'.(!empty($conf->global->MAIN_MAIL_SMTP_SERVER) ? $conf->global->MAIN_MAIL_SMTP_SERVER : '').'</td></tr>';
@@ -687,31 +690,31 @@ if ($action == 'edit') {
 
 
 		// Port
-		if ($linuxlike && (isset($conf->global->MAIN_MAIL_SENDMODE) && $conf->global->MAIN_MAIL_SENDMODE == 'mail')) {
+		if ($linuxlike && (getDolGlobalString('MAIN_MAIL_SENDMODE') == 'mail')) {
 			print '<tr class="oddeven"><td>'.$langs->trans("MAIN_MAIL_SMTP_PORT_NotAvailableOnLinuxLike").'</td><td><span class="opacitymedium">'.$langs->trans("SeeLocalSendMailSetup").'</span></td></tr>';
 		} else {
 			print '<tr class="oddeven"><td>'.$langs->trans("MAIN_MAIL_SMTP_PORT", ini_get('smtp_port') ?ini_get('smtp_port') : $langs->transnoentities("Undefined")).'</td><td>'.(!empty($conf->global->MAIN_MAIL_SMTP_PORT) ? $conf->global->MAIN_MAIL_SMTP_PORT : '').'</td></tr>';
 		}
 
 		// SMTPS ID
-		if (isset($conf->global->MAIN_MAIL_SENDMODE) && in_array($conf->global->MAIN_MAIL_SENDMODE, array('smtps', 'swiftmailer'))) {
+		if (in_array(getDolGlobalString('MAIN_MAIL_SENDMODE'), array('smtps', 'swiftmailer'))) {
 			print '<tr class="oddeven"><td>'.$langs->trans("MAIN_MAIL_SMTPS_ID").'</td><td>'.$conf->global->MAIN_MAIL_SMTPS_ID.'</td></tr>';
 		}
 
 		// AUTH method
-		if (isset($conf->global->MAIN_MAIL_SENDMODE) && in_array($conf->global->MAIN_MAIL_SENDMODE, array('smtps'))) {
-			$authtype = $conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE;
+		if (in_array(getDolGlobalString('MAIN_MAIL_SENDMODE'), array('smtps', 'swiftmailer'))) {
+			$authtype = getDolGlobalString('MAIN_MAIL_SMTPS_AUTH_TYPE', 'LOGIN');
 			$text = ($authtype === "LOGIN") ? $langs->trans("UsePassword") : ($authtype === "XOAUTH2" ?  $langs->trans("UseOauth") : '') ;
 			print '<tr class="oddeven"><td>'.$langs->trans("MAIN_MAIL_SMTPS_AUTH_TYPE").'</td><td>'.$text.'</td></tr>';
 		}
 
 		// SMTPS PW
-		if (isset($conf->global->MAIN_MAIL_SENDMODE) && (in_array($conf->global->MAIN_MAIL_SENDMODE, array('swiftmailer')) || (in_array($conf->global->MAIN_MAIL_SENDMODE, array('smtps')) && (isset($conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE) && $conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE === "LOGIN")))) {
+		if (in_array(getDolGlobalString('MAIN_MAIL_SENDMODE'), array('smtps', 'swiftmailer')) && getDolGlobalString('MAIN_MAIL_SMTPS_AUTH_TYPE') != "XOAUTH2") {
 			print '<tr class="oddeven"><td>'.$langs->trans("MAIN_MAIL_SMTPS_PW").'</td><td>'.preg_replace('/./', '*', $conf->global->MAIN_MAIL_SMTPS_PW).'</td></tr>';
 		}
 
 		// SMTPS oauth service
-		if (isset($conf->global->MAIN_MAIL_SENDMODE) && in_array($conf->global->MAIN_MAIL_SENDMODE, array('smtps')) && isset($conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE) && $conf->global->MAIN_MAIL_SMTPS_AUTH_TYPE === "XOAUTH2") {
+		if (in_array(getDolGlobalString('MAIN_MAIL_SENDMODE'), array('smtps', 'swiftmailer')) && getDolGlobalString('MAIN_MAIL_SMTPS_AUTH_TYPE') === "XOAUTH2") {
 			$text = $oauthservices[$conf->global->MAIN_MAIL_SMTPS_OAUTH_SERVICE];
 			if (empty($text)) {
 				$text = $langs->trans("Undefined").img_warning();
diff --git a/htdocs/core/actions_sendmails.inc.php b/htdocs/core/actions_sendmails.inc.php
index 7494f5a3668..3749b403469 100644
--- a/htdocs/core/actions_sendmails.inc.php
+++ b/htdocs/core/actions_sendmails.inc.php
@@ -427,9 +427,14 @@ if (($action == 'send' || $action == 'relance') && !GETPOST('addfile') && !GETPO
 				} else {
 					$langs->load("other");
 					$mesg = '<div class="error">';
-					if ($mailfile->error) {
+					if (!empty($mailfile->error) || !empty($mailfile->errors)) {
 						$mesg .= $langs->transnoentities('ErrorFailedToSendMail', dol_escape_htmltag($from), dol_escape_htmltag($sendto));
-						$mesg .= '<br>'.$mailfile->error;
+						if (!empty($mailfile->error)) {
+							$mesg .= '<br>'.$mailfile->error;
+						}
+						if (!empty($mailfile->errors) && is_array($mailfile->errors)) {
+							$mesg .= '<br>'.implode('<br>', $mailfile->errors);
+						}
 					} else {
 						$mesg .= $langs->transnoentities('ErrorFailedToSendMail', dol_escape_htmltag($from), dol_escape_htmltag($sendto));
 						if (!empty($conf->global->MAIN_DISABLE_ALL_MAILS)) {
diff --git a/htdocs/core/class/CMailFile.class.php b/htdocs/core/class/CMailFile.class.php
index 1b03ed0d604..54573f92c7a 100644
--- a/htdocs/core/class/CMailFile.class.php
+++ b/htdocs/core/class/CMailFile.class.php
@@ -72,9 +72,29 @@ class CMailFile
 	 */
 	public $error = '';
 
+	/**
+	 * @var string[] Array of Error code (or message)
+	 */
+	public $errors = array();
+
 	public $smtps; // Contains SMTPs object (if this method is used)
 	public $phpmailer; // Contains PHPMailer object (if this method is used)
 
+	/**
+	 * @var Swift_SmtpTransport
+	 */
+	public $transport;
+
+	/**
+	 * @var Swift_Mailer
+	 */
+	public $mailer;
+
+	/**
+	 * @var Swift_Plugins_Loggers_ArrayLogger
+	 */
+	public $logger;
+
 	/**
 	 * @var string CSS
 	 */
@@ -847,7 +867,7 @@ class CMailFile
 					$this->smtps->setPW($loginpass);
 				}
 
-				if (!empty($conf->global->$keyforsmtpauthtype) && $conf->global->$keyforsmtpauthtype === "XOAUTH2") {
+				if (getDolGlobalString($keyforsmtpauthtype) === "XOAUTH2") {
 					require_once DOL_DOCUMENT_ROOT.'/core/lib/oauth.lib.php'; // define $supportedoauth2array
 					$keyforsupportedoauth2array = $conf->global->$keyforsmtpoauthservice;
 					if (preg_match('/^.*-/', $keyforsupportedoauth2array)) {
@@ -897,7 +917,6 @@ class CMailFile
 					}
 
 					$result = $this->smtps->sendMsg();
-					//print $result;
 
 					if (!empty($conf->global->MAIN_MAIL_DEBUG)) {
 						$this->dump_mail();
@@ -943,9 +962,39 @@ class CMailFile
 				if (!empty($conf->global->$keyforsmtpid)) {
 					$this->transport->setUsername($conf->global->$keyforsmtpid);
 				}
-				if (!empty($conf->global->$keyforsmtppw)) {
+				if (!empty($conf->global->$keyforsmtppw) && getDolGlobalString($keyforsmtpauthtype) != "XOAUTH2") {
 					$this->transport->setPassword($conf->global->$keyforsmtppw);
 				}
+				if (getDolGlobalString($keyforsmtpauthtype) === "XOAUTH2") {
+					require_once DOL_DOCUMENT_ROOT.'/core/lib/oauth.lib.php'; // define $supportedoauth2array
+					$keyforsupportedoauth2array = getDolGlobalString($keyforsmtpoauthservice);
+					if (preg_match('/^.*-/', $keyforsupportedoauth2array)) {
+						$keyforprovider = preg_replace('/^.*-/', '', $keyforsupportedoauth2array);
+					} else {
+						$keyforprovider = '';
+					}
+					$keyforsupportedoauth2array = preg_replace('/-.*$/', '', $keyforsupportedoauth2array);
+					$keyforsupportedoauth2array = 'OAUTH_'.$keyforsupportedoauth2array.'_NAME';
+
+					$OAUTH_SERVICENAME = (empty($supportedoauth2array[$keyforsupportedoauth2array]['name']) ? 'Unknown' : $supportedoauth2array[$keyforsupportedoauth2array]['name'].($keyforprovider ? '-'.$keyforprovider : ''));
+
+					require_once DOL_DOCUMENT_ROOT.'/includes/OAuth/bootstrap.php';
+
+					$storage = new DoliStorage($db, $conf);
+					try {
+						$tokenobj = $storage->retrieveAccessToken($OAUTH_SERVICENAME);
+						if (is_object($tokenobj)) {
+							$this->transport->setAuthMode('XOAUTH2');
+							$this->transport->setPassword($tokenobj->getAccessToken());
+						} else {
+							$this->errors[] = "Token not found";
+						}
+					} catch (Exception $e) {
+						// Return an error if token not found
+						$this->errors[] = $e->getMessage();
+						dol_syslog("CMailFile::sendfile: mail end error=".$e->getMessage(), LOG_ERR);
+					}
+				}
 				if (!empty($conf->global->$keyforsslseflsigned)) {
 					$this->transport->setStreamOptions(array('ssl' => array('allow_self_signed' => true, 'verify_peer' => false)));
 				}
@@ -978,16 +1027,16 @@ class CMailFile
 				try {
 					$result = $this->mailer->send($this->message, $failedRecipients);
 				} catch (Exception $e) {
-					$this->error = $e->getMessage();
+					$this->errors[] = $e->getMessage();
 				}
 				if (!empty($conf->global->MAIN_MAIL_DEBUG)) {
 					$this->dump_mail();
 				}
 
 				$res = true;
-				if (!empty($this->error) || !$result) {
+				if (!empty($this->error) || !empty($this->errors) || !$result) {
 					if (!empty($failedRecipients)) {
-						$this->error = 'Transport failed for the following addresses: "' . join('", "', $failedRecipients) . '".';
+						$this->errors[] = 'Transport failed for the following addresses: "' . join('", "', $failedRecipients) . '".';
 					}
 					dol_syslog("CMailFile::sendfile: mail end error=".$this->error, LOG_ERR);
 					$res = false;
diff --git a/htdocs/langs/fr_FR/admin.lang b/htdocs/langs/fr_FR/admin.lang
index 42d973e8e06..18c2dfc615d 100644
--- a/htdocs/langs/fr_FR/admin.lang
+++ b/htdocs/langs/fr_FR/admin.lang
@@ -2291,5 +2291,5 @@ OauthNotAvailableForAllAndHadToBeCreatedBefore=L'authentification OAUTH2 n'est p
 MAIN_MAIL_SMTPS_OAUTH_SERVICE=Service d'authentification OAUTH2
 DontForgetCreateTokenOauthMod=Un jeton avec les bonnes permissions doit avoir été créé en amont avec le module OAUTH
 MAIN_MAIL_SMTPS_AUTH_TYPE=Méthode d'authentication
-UsePassword=Utiliser un mot de pass
-UseOauth=Utiliser un jeton d'authentification OAUTH
\ No newline at end of file
+UsePassword=Utiliser un mot de passe
+UseOauth=Utiliser un jeton d'authentification OAUTH