diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 4776df4982e..4adf9430f02 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -1237,7 +1237,7 @@ protected function _prep_q_encoding($str, $from = FALSE)
 
 		// wrap each line with the shebang, charset, and transfer encoding
 		// the preceding space on successive lines is required for header "folding"
-		return trim(preg_replace('/^(.*)$/m', ' =?'.$this->charset.'?Q?$1?=', $output.$temp));
+		return trim(preg_replace('/^(.*?)(\r*)$/m', ' =?'.$this->charset.'?Q?$1?=$2', $output.$temp));
 	}
 
 	// --------------------------------------------------------------------
@@ -1861,4 +1861,4 @@ protected function _mime_types($ext = '')
 }
 
 /* End of file Email.php */
-/* Location: ./system/libraries/Email.php */
\ No newline at end of file
+/* Location: ./system/libraries/Email.php */
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 47429aed314..50bf2c3049a 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -243,6 +243,7 @@ Release Date: Not Released
 Bug fixes for 3.0
 ------------------
 
+-  Fixed a bug (#1709) where the email headers were broken when using long email subjects and \r\n as crlf.
 -  Fixed a bug where ``unlink()`` raised an error if cache file did not exist when you try to delete it.
 -  Fixed a bug (#181) where a mis-spelling was in the form validation language file.
 -  Fixed a bug (#159, #163) that mishandled Query Builder nested transactions because _trans_depth was not getting incremented.