Fix invalid Content-Type header when send_format_flowed=false (#1489992)

2 files changed, 15 insertions, 14 deletions

diff --git a/program/lib/Mail/mime.php b/program/lib/Mail/mime.php
index 50297dd3e..db0fd1fc2 100644
--- a/program/lib/Mail/mime.php
+++ b/program/lib/Mail/mime.php
@@ -1387,19 +1387,24 @@ class Mail_mime
 
         if ($headers['Content-Type'] == 'text/plain') {
             // single-part message: add charset and encoding
-            $charset = 'charset=' . $this->_build_params['text_charset'];
-            // place charset parameter in the same line, if possible
-            // 26 = strlen("Content-Type: text/plain; ")
-            $headers['Content-Type']
-                .= (strlen($charset) + 26 <= 76) ? "; $charset" : ";$eol $charset";
+            if ($this->_build_params['text_charset']) {
+                $charset = 'charset=' . $this->_build_params['text_charset'];
+                // place charset parameter in the same line, if possible
+                // 26 = strlen("Content-Type: text/plain; ")
+                $headers['Content-Type']
+                    .= (strlen($charset) + 26 <= 76) ? "; $charset" : ";$eol $charset";
+            }
+
             $headers['Content-Transfer-Encoding']
                 = $this->_build_params['text_encoding'];
         } else if ($headers['Content-Type'] == 'text/html') {
             // single-part message: add charset and encoding
-            $charset = 'charset=' . $this->_build_params['html_charset'];
-            // place charset parameter in the same line, if possible
-            $headers['Content-Type']
-                .= (strlen($charset) + 25 <= 76) ? "; $charset" : ";$eol $charset";
+            if ($this->_build_params['html_charset']) {
+                $charset = 'charset=' . $this->_build_params['html_charset'];
+                // place charset parameter in the same line, if possible
+                $headers['Content-Type']
+                    .= (strlen($charset) + 25 <= 76) ? "; $charset" : ";$eol $charset";
+            }
             $headers['Content-Transfer-Encoding']
                 = $this->_build_params['html_encoding'];
         } else {
diff --git a/program/steps/mail/sendmail.inc b/program/steps/mail/sendmail.inc
index 13a8a24a9..6c4006426 100644
--- a/program/steps/mail/sendmail.inc
+++ b/program/steps/mail/sendmail.inc
@@ -467,15 +467,11 @@ if (preg_match('/[^\x00-\x7F]/', $MAIL_MIME->getTXTBody())) {
     $transfer_encoding = $RCMAIL->config->get('force_7bit') ? 'quoted-printable' : '8bit';
 }
 else {
-    $text_charset      = '';
+    $text_charset      = 'US-ASCII';
     $transfer_encoding = '7bit';
 }
 
 if ($flowed) {
-    if (!$text_charset) {
-        $text_charset = 'US-ASCII';
-    }
-
     $text_charset .= ";\r\n format=flowed";
 }