diff --git a/htdocs/core/class/CMailFile.class.php b/htdocs/core/class/CMailFile.class.php
index 4396378a792..5726b02ac84 100644
--- a/htdocs/core/class/CMailFile.class.php
+++ b/htdocs/core/class/CMailFile.class.php
@@ -992,7 +992,26 @@ class CMailFile
 						$this->dump_mail();
 					}
 
-					$result = $this->smtps->getErrors();
+					if (! $result) {
+						$smtperrorcode = $this->smtps->lastretval;	// SMTP error code
+						dol_syslog("CMailFile::sendfile: mail SMTP error code ".$smtperrorcode, LOG_WARNING);
+
+						if ($smtperrorcode == '421') {	// Try later
+							// TODO Add a delay and try again
+							/*
+							dol_syslog("CMailFile::sendfile: Try later error, so we wait and we retry");
+							sleep(2);
+
+							$result = $this->smtps->sendMsg();
+
+							if (!empty($conf->global->MAIN_MAIL_DEBUG)) {
+								$this->dump_mail();
+							}
+							*/
+						}
+					}
+
+					$result = $this->smtps->getErrors();	// applicative error code (not SMTP error code)
 					if (empty($this->error) && empty($result)) {
 						dol_syslog("CMailFile::sendfile: mail end success", LOG_DEBUG);
 						$res = true;
@@ -1262,7 +1281,11 @@ class CMailFile
 
 		if (@is_writeable($dolibarr_main_data_root)) {	// Avoid fatal error on fopen with open_basedir
 			$srcfile = $dolibarr_main_data_root."/dolibarr_mail.log";
-			$destfile = $dolibarr_main_data_root."/dolibarr_mail.err";
+			if (getDolGlobalString('MAIN_MAIL_DEBUG_ERR_WITH_DATE')) {
+				$destfile = $dolibarr_main_data_root."/dolibarr_mail.".dol_print_date(dol_now(), 'dayhourlog', 'gmt').".err";
+			} else {
+				$destfile = $dolibarr_main_data_root."/dolibarr_mail.err";
+			}
 
 			dol_move($srcfile, $destfile, 0, 1, 0, 0);
 		}
diff --git a/htdocs/core/class/smtps.class.php b/htdocs/core/class/smtps.class.php
index 135d9d9e8de..549ea8d02fc 100644
--- a/htdocs/core/class/smtps.class.php
+++ b/htdocs/core/class/smtps.class.php
@@ -228,6 +228,7 @@ class SMTPs
 
 	// @CHANGE LDR
 	public $log = '';
+	public $lastretval = '';
 	private $_errorsTo = '';
 	private $_deliveryReceipt = 0;
 	private $_trackId = '';
@@ -670,10 +671,11 @@ class SMTPs
 					}
 				}
 
+				// Send the HELO message to the SMTP server
 				$_retVal = $this->socket_send_str('HELO '.$hosth, '250');
 			}
 
-			// Well, did we get to the server?
+			// Well, did we get the server answer with correct code ?
 			if ($_retVal) {
 				// From this point onward most server response codes should be 250
 				// Specify who the mail is from....
@@ -716,8 +718,11 @@ class SMTPs
 
 				// Now tell the server we are done and close the socket...
 				fputs($this->socket, 'QUIT');
-				fclose($this->socket);
+			} else {
+				// We got code $this->lastretval
 			}
+
+			fclose($this->socket);
 		}
 
 		return $_retVal;
@@ -1870,7 +1875,9 @@ class SMTPs
 	 * using SMTP Extensions
 	 *
 	 * @param	resource    $socket			Socket handler
-	 * @param	string		$response		Response. Example: "550 5.7.1  https://support.google.com/a/answer/6140680#invalidcred j21sm814390wre.3"
+	 * @param	string		$response		Expected response ('250', ...). Example of response we can get:
+	 * 										"421 4.7.0 Try again later, closing connection. (EHLO) nb21-20020a1709071c9500b0093d0d964affsm869534ejc.73 - gsmtp"
+	 * 										"550 5.7.1  https://support.google.com/a/answer/6140680#invalidcred j21sm814390wre.3"
 	 * @return	boolean						True or false
 	 */
 	public function server_parse($socket, $response)
@@ -1897,8 +1904,10 @@ class SMTPs
 			$limit++;
 		}
 
+		$this->lastretval = substr($server_response, 0, 3);
+
 		if (!(substr($server_response, 0, 3) == $response)) {
-			$this->_setErr(120, "Ran into problems sending Mail.\r\nResponse:".$server_response);
+			$this->_setErr(120, "Ran into problems sending Mail.\r\nResponse: ".$server_response);
 			$_retVal = false;
 		}
 
@@ -1910,9 +1919,9 @@ class SMTPs
 	 * Send str
 	 *
 	 * @param	string		$_strSend		String to send
-	 * @param 	string		$_returnCode	Return code
+	 * @param 	string		$_returnCode	Expected return code
 	 * @param 	string		$CRLF			CRLF
-	 * @return 	boolean|null						True or false
+	 * @return 	boolean|null				True or false
 	 */
 	public function socket_send_str($_strSend, $_returnCode = null, $CRLF = "\r\n")
 	{
@@ -1928,6 +1937,8 @@ class SMTPs
 		if ($_returnCode) {
 			return $this->server_parse($this->socket, $_returnCode);
 		}
+
+		return null;
 	}
 
 	// =============================================================
@@ -1949,7 +1960,7 @@ class SMTPs
 	}
 
 	/**
-	 * Returns errors codes and messages for Class
+	 * Returns applicative errors codes and messages for Class (not the SMTP error code)
 	 *
 	 * @return string $_errMsg  Error Message
 	 */