Fix #4073
diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 459c8f5..acf3629 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -1869,20 +1869,26 @@
 			return FALSE;
 		}
 
-		$this->_send_command('from', $this->clean_email($this->_headers['From']));
+		if ( ! $this->_send_command('from', $this->clean_email($this->_headers['From'])))
+		{
+			return FALSE;
+		}
 
 		foreach ($this->_recipients as $val)
 		{
-			$this->_send_command('to', $val);
+			if ( ! $this->_send_command('to', $val))
+			{
+				return FALSE;
+			}
 		}
 
 		if (count($this->_cc_array) > 0)
 		{
 			foreach ($this->_cc_array as $val)
 			{
-				if ($val !== '')
+				if ($val !== '' && ! $this->_send_command('to', $val))
 				{
-					$this->_send_command('to', $val);
+					return FALSE;
 				}
 			}
 		}
@@ -1891,14 +1897,17 @@
 		{
 			foreach ($this->_bcc_array as $val)
 			{
-				if ($val !== '')
+				if ($val !== '' && ! $this->_send_command('to', $val))
 				{
-					$this->_send_command('to', $val);
+					return FALSE;
 				}
 			}
 		}
 
-		$this->_send_command('data');
+		if ( ! $this->_send_command('data'))
+		{
+			return FALSE;
+		}
 
 		// perform dot transformation on any lines that begin with a dot
 		$this->_send_data($this->_header_str.preg_replace('/^\./m', '..$1', $this->_finalbody));