diff --git a/htdocs/admin/mails.php b/htdocs/admin/mails.php
index 53937687b5732..148fcf7626869 100644
--- a/htdocs/admin/mails.php
+++ b/htdocs/admin/mails.php
@@ -230,7 +230,6 @@
 if (preg_match('/^win/i',PHP_OS)) $linuxlike=0;
 if (preg_match('/^mac/i',PHP_OS)) $linuxlike=0;
 
-
 if (empty($conf->global->MAIN_MAIL_SENDMODE)) $conf->global->MAIN_MAIL_SENDMODE='mail';
 $port=! empty($conf->global->MAIN_MAIL_SMTP_PORT)?$conf->global->MAIN_MAIL_SMTP_PORT:ini_get('smtp_port');
 if (! $port) $port=25;
@@ -275,8 +274,21 @@ function initfields()
                             ';
 		if ($linuxlike)
 		{
-			print '         jQuery("#MAIN_MAIL_SMTP_SERVER").prop("disabled", true);';
-			print '         jQuery("#MAIN_MAIL_SMTP_PORT").prop("disabled", true);';
+			print '
+			               jQuery("#MAIN_MAIL_SMTP_SERVER").hide();
+			               jQuery("#MAIN_MAIL_SMTP_PORT").hide();
+			               jQuery("#smtp_server_mess").show();
+			               jQuery("#smtp_port_mess").show();
+			               ';
+		}
+		else
+		{
+			print '
+			               jQuery("#MAIN_MAIL_SMTP_SERVER").prop("disabled", true);
+			               jQuery("#MAIN_MAIL_SMTP_PORT").prop("disabled", true);
+			               jQuery("#smtp_server_mess").hide();
+			               jQuery("#smtp_port_mess").hide();
+			               ';
 		}
 		print '
                         }
@@ -287,7 +299,11 @@ function initfields()
                             jQuery("#MAIN_MAIL_EMAIL_TLS").removeAttr("disabled");
                             jQuery("#MAIN_MAIL_SMTP_SERVER").removeAttr("disabled");
                             jQuery("#MAIN_MAIL_SMTP_PORT").removeAttr("disabled");
-                        }
+                            jQuery("#MAIN_MAIL_SMTP_SERVER").show();
+                            jQuery("#MAIN_MAIL_SMTP_PORT").show();
+                            jQuery("#smtp_server_mess").hide();
+			                jQuery("#smtp_port_mess").hide();
+						}
                     }
                     initfields();
                     jQuery("#MAIN_MAIL_SENDMODE").change(function() {
@@ -336,7 +352,7 @@ function initfields()
 	}
 	print '</td></tr>';
 
-	// Server
+	// Host server
 	$var=!$var;
 	print '<tr '.$bc[$var].'><td>';
 	if (! $conf->use_javascript_ajax && $linuxlike && $conf->global->MAIN_MAIL_SENDMODE == 'mail')
@@ -357,6 +373,7 @@ function initfields()
 		{
 			print '<input class="flat" id="MAIN_MAIL_SMTP_SERVER" name="MAIN_MAIL_SMTP_SERVER" size="18" value="' . $mainserver . '">';
 			print '<input type="hidden" id="MAIN_MAIL_SMTP_SERVER_sav" name="MAIN_MAIL_SMTP_SERVER_sav" value="' . $mainserver . '">';
+			print '<span id="smtp_server_mess">'.$langs->trans("SeeLocalSendMailSetup").'</span>';
 		}
 		else
 		{
@@ -389,6 +406,7 @@ function initfields()
 		{
 			print '<input class="flat" id="MAIN_MAIL_SMTP_PORT" name="MAIN_MAIL_SMTP_PORT" size="3" value="' . $mainport . '">';
 			print '<input type="hidden" id="MAIN_MAIL_SMTP_PORT_sav" name="MAIN_MAIL_SMTP_PORT_sav" value="' . $mainport . '">';
+			print '<span id="smtp_port_mess">'.$langs->trans("SeeLocalSendMailSetup").'</span>';
 		}
 		else
 		{
@@ -509,7 +527,7 @@ function initfields()
 	print $text;
 	print '</td></tr>';
 
-	// Server
+	// Host server
 	$var=!$var;
 	if ($linuxlike && (isset($conf->global->MAIN_MAIL_SENDMODE) && $conf->global->MAIN_MAIL_SENDMODE == 'mail'))
 	{
diff --git a/htdocs/core/class/CMailFile.class.php b/htdocs/core/class/CMailFile.class.php
index 1aadc47b79ee1..ef6d27b59b1ee 100644
--- a/htdocs/core/class/CMailFile.class.php
+++ b/htdocs/core/class/CMailFile.class.php
@@ -39,7 +39,7 @@ class CMailFile
 	var $subject;      	// Topic:       Subject of email
 	var $addr_from;    	// From:		Label and EMail of sender (must include '<>'). For example '<myemail@example.com>' or 'John Doe <myemail@example.com>' or '<myemail+trackingid@example.com>')
 	                   	// Sender:      Who send the email ("Sender" has sent emails on behalf of "From").
-	                   	//              Use it when the "From" is an email of a domain that is a SPF protected domain, and sending smtp server is not this domain. In such case, use for Sender an email of the protected domain.
+	                   	//              Use it when the "From" is an email of a domain that is a SPF protected domain, and sending smtp server is not this domain. In such case, add Sender field with an email of the protected domain.
 	                   	// Return-Path: Email where to send bounds.
 	var $errors_to;		// Errors-To:	Email where to send errors.
 	var $addr_to;
@@ -408,8 +408,8 @@ function sendfile()
 					$bounce = '';	// By default
 					if (! empty($conf->global->MAIN_MAIL_ALLOW_SENDMAIL_F))
 					{
-						// le return-path dans les header ne fonctionne pas avec tous les MTA
-						// Le passage par -f est donc possible si la constante MAIN_MAIL_ALLOW_SENDMAIL_F est definie.
+						// le "Return-Path" (retour des messages bounced) dans les header ne fonctionne pas avec tous les MTA
+						// Le forcage de la valeure grace à l'option -f de sendmail est donc possible si la constante MAIN_MAIL_ALLOW_SENDMAIL_F est definie.
 						// La variable definie pose des pb avec certains sendmail securisee (option -f refusee car dangereuse)
 						$bounce .= ($bounce?' ':'').(! empty($conf->global->MAIN_MAIL_ERRORS_TO) ? '-f' . $this->getValidAddress($conf->global->MAIN_MAIL_ERRORS_TO,2) : ($this->addr_from != '' ? '-f' . $this->getValidAddress($this->addr_from,2) : '') );
 					}
@@ -427,7 +427,15 @@ function sendfile()
 
 					if (! $res)
 					{
-						$this->error="Failed to send mail with php mail to HOST=".ini_get('SMTP').", PORT=".ini_get('smtp_port')."<br>Check your server logs and your firewalls setup";
+						$this->error="Failed to send mail with php mail";
+						$linuxlike=1;
+						if (preg_match('/^win/i',PHP_OS)) $linuxlike=0;
+						if (preg_match('/^mac/i',PHP_OS)) $linuxlike=0;
+						if (! $linuxlike)
+						{
+							$this->error.=" to HOST=".ini_get('SMTP').", PORT=".ini_get('smtp_port');	// This values are value used only for non linuxlike systems
+						}
+						$this->error.=".<br>Check your server logs and your firewalls setup";
 						dol_syslog("CMailFile::sendfile: mail end error=".$this->error, LOG_ERR);
 					}
 					else