diff --git a/htdocs/core/class/CMailFile.class.php b/htdocs/core/class/CMailFile.class.php
index e0a1fd35092..dc2b00c586c 100644
--- a/htdocs/core/class/CMailFile.class.php
+++ b/htdocs/core/class/CMailFile.class.php
@@ -82,15 +82,15 @@ class CMailFile
     public $headers;
     public $message;
     /**
-	 * @var array fullfilenames list
+	 * @var array fullfilenames list (full path of filename on file system)
 	 */
 	public $filename_list = array();
 	/**
-	 * @var array mimetypes of files list
+	 * @var array mimetypes of files list (List of MIME type of attached files)
 	 */
 	public $mimetype_list = array();
 	/**
-	 * @var array filenames list
+	 * @var array filenames list (List of attached file name in message)
 	 */
 	public $mimefilename_list = array();
 
@@ -137,7 +137,14 @@ class CMailFile
 	{
 		global $conf, $dolibarr_main_data_root;
 
-        $this->subject = $subject;
+		// Clean values of $mimefilename_list
+		if (is_array($mimefilename_list)) {
+			foreach($mimefilename_list as $key => $val) {
+				$mimefilename_list[$key] = dol_string_unaccent($mimefilename_list[$key]);
+			}
+		}
+
+		$this->subject = $subject;
 		$this->addr_to = $to;
 		$this->addr_from = $from;
 		$this->msg = $msg;
@@ -156,7 +163,6 @@ class CMailFile
 		$this->mimetype_list = $mimetype_list;
 		$this->mimefilename_list = $mimefilename_list;
 
-
 		// Define this->sendmode
 		$this->sendmode = '';
 		if ($this->sendcontext == 'emailing' && !empty($conf->global->MAIN_MAIL_SENDMODE_EMAILING) && $conf->global->MAIN_MAIL_SENDMODE_EMAILING != 'default')
@@ -323,7 +329,13 @@ class CMailFile
 			$smtps = new SMTPs();
 			$smtps->setCharSet($conf->file->character_set_client);
 
-			$smtps->setSubject($this->encodetorfc2822($subject));
+			// Encode subject if required.
+			$subjecttouse = $subject;
+			if (! ascii_check($subjecttouse)) {
+				$subjecttouse = $this->encodetorfc2822($subjecttouse);
+			}
+
+			$smtps->setSubject($subjecttouse);
 			$smtps->setTO($this->getValidAddress($to, 0, 1));
 			$smtps->setFrom($this->getValidAddress($from, 0, 1));
 			$smtps->setTrackId($trackid);
@@ -669,8 +681,14 @@ class CMailFile
 
 					if (!empty($conf->global->MAIN_MAIL_DEBUG)) $this->dump_mail();
 
-					if (!empty($additionnalparam)) $res = mail($dest, $this->encodetorfc2822($this->subject), $this->message, $this->headers, $additionnalparam);
-					else $res = mail($dest, $this->encodetorfc2822($this->subject), $this->message, $this->headers);
+					// Encode subject if required.
+					$subjecttouse = $this->subject;
+					if (! ascii_check($subjecttouse)) {
+						$subjecttouse = $this->encodetorfc2822($subjecttouse);
+					}
+
+					if (!empty($additionnalparam)) $res = mail($dest, $subjecttouse, $this->message, $this->headers, $additionnalparam);
+					else $res = mail($dest, $subjecttouse, $this->message, $this->headers);
 
 					if (!$res)
 					{
diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index 1c4a55e6c09..da82a81ea83 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -6911,6 +6911,24 @@ function utf8_check($str)
 	return true;
 }
 
+/**
+ *      Check if a string is in ASCII
+ *
+ *      @param	string	$str        String to check
+ * 		@return	boolean				True if string is ASCII, False if not (byte value > 0x7F)
+ */
+function ascii_check($str)
+{
+	if (function_exists('mb_check_encoding')) {
+		//if (mb_detect_encoding($str, 'ASCII', true) return false;
+		if (! mb_check_encoding($str, 'ASCII')) return false;
+	} else {
+		if (preg_match('/[^\x00-\x7f]/', $str)) return false;	// Contains a byte > 7f
+	}
+
+	return true;
+}
+
 
 /**
  *      Return a string encoded into OS filesystem encoding. This function is used to define
diff --git a/test/phpunit/FunctionsLibTest.php b/test/phpunit/FunctionsLibTest.php
index 12126d9cf40..dff6b3a7d06 100644
--- a/test/phpunit/FunctionsLibTest.php
+++ b/test/phpunit/FunctionsLibTest.php
@@ -679,6 +679,26 @@ class FunctionsLibTest extends PHPUnit\Framework\TestCase
         $this->assertFalse($result);
     }
 
+    /**
+     * testDolAsciiCheck
+     *
+     * @return void
+     */
+    public function testDolAsciiCheck()
+    {
+    	// True
+    	$result=ascii_check('azerty');
+    	$this->assertTrue($result);
+
+    	$result=ascii_check('é');
+    	$this->assertFalse($result);
+
+    	$file=dirname(__FILE__).'/textutf8.txt';
+    	$filecontent=file_get_contents($file);
+    	$result=ascii_check($filecontent);
+    	$this->assertFalse($result);
+    }
+
     /**
      * testDolTrunc
      *