diff -r 17eb29faebde Lib/smtpd.py
--- a/Lib/smtpd.py	Sat Apr 04 23:35:52 2015 +0300
+++ b/Lib/smtpd.py	Sun Apr 05 00:45:34 2015 +0100
@@ -462,7 +462,7 @@
 
     def smtp_HELP(self, arg):
         if arg:
-            extended = ' [SP <mail parameters]'
+            extended = ' [SP <mail-parameters>]'
             lc_arg = arg.upper()
             if lc_arg == 'EHLO':
                 self.push('250 Syntax: EHLO hostname')