Backport 58618:

Issue 1307 by Derek Shockey, fix the same bug for RCPT.

diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index 4aa34763ecff0a2fa84af1d3561666ba2939e3ef..e09774f2d9bdfed0260456fb824cc5a1c3dee21d 100755 (executable)
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -237,7 +237,7 @@ class SMTPChannel(asynchat.async_chat):
         if not self.__mailfrom:
             self.push('503 Error: need MAIL command')
             return
-        address = self.__getaddr('TO:', arg)
+        address = self.__getaddr('TO:', arg) if arg else None
         if not address:
             self.push('501 Syntax: RCPT TO: <address>')
             return