diff --git a/lisp/mail/smtpmail.el b/lisp/mail/smtpmail.el
index 741c4393e6..d9930491d9 100644
--- a/lisp/mail/smtpmail.el
+++ b/lisp/mail/smtpmail.el
@@ -658,10 +658,12 @@ smtpmail-user-mail-address
 	      user-mail-address))))
 
 (defun smtpmail-via-smtp (recipient smtpmail-text-buffer
-				    &optional ask-for-password)
+				    &optional ask-for-password
+                                    send-attempts)
   (unless smtpmail-smtp-server
     (smtpmail-query-smtp-server))
   (let ((process nil)
+        (send-attempts (or send-attempts 1))
 	(host (or smtpmail-smtp-server
 		  (error "`smtpmail-smtp-server' not defined")))
 	(port smtpmail-smtp-service)
@@ -817,6 +819,20 @@ smtpmail-via-smtp
 	       ((smtpmail-ok-p (setq result (smtpmail-read-response process)))
 		;; Success.
 		)
+               ((and (numberp (car result))
+                     (<= 400 (car result) 499)
+                     (< send-attempts 10))
+                ;; Retry on getting a transient 4xx code; see
+                ;; https://tools.ietf.org/html/rfc5321#section-4.2.1
+                (ignore-errors
+		  (smtpmail-send-command process "QUIT")
+		  (smtpmail-read-response process))
+		(delete-process process)
+		(setq process nil)
+		(throw 'done
+		       (smtpmail-via-smtp recipient smtpmail-text-buffer
+                                          ask-for-password
+                                          (1+ send-attempts))))
 	       ((and auth-mechanisms
 		     (not ask-for-password)
 		     (eq (car result) 530))