FIX Filenames must not contains non ascii char or we will get non ascii

char into the SMTP header.
FIX Do not encode subject if it is full ascii (not required)

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)
 					{

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

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
      *