Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 11438)
+++ wp-includes/pluggable.php	(working copy)
@@ -249,9 +249,10 @@
  * @param string $message Message contents
  * @param string|array $headers Optional. Additional headers.
  * @param string|array $attachments Optional. Files to attach.
+ * @param bool $preserve_quotes Optional. Preserve encoded quotes in plain text emails.
  * @return bool Whether the email contents were sent successfully.
  */
-function wp_mail( $to, $subject, $message, $headers = '', $attachments = array() ) {
+function wp_mail( $to, $subject, $message, $headers = '', $attachments = array(), $preserve_quotes = false ) {
 	// Compact the input, apply the filters, and extract them back out
 	extract( apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers', 'attachments' ) ) );
 
@@ -337,6 +338,14 @@
 		}
 	}
 
+	if ( $preserve_quotes != true && ( !isset( $content_type ) || $content_type = 'text/plain' ) ) {
+		// Ensure we don't send encoded quotes in plain text emails
+		$encoded_quotes = array( '"', ''' );
+		$decoded_quotes = array( '"', "'" );
+		$subject = str_replace( $encoded_quotes, $decoded_quotes, $subject );
+		$message = str_replace( $encoded_quotes, $decoded_quotes, $message );
+	}
+
 	// Empty out the values that may be set
 	$phpmailer->ClearAddresses();
 	$phpmailer->ClearAllRecipients();