diff --git a/lisp/mail/smtpmail.el b/lisp/mail/smtpmail.el
index 802c9ba788d..9cf28fbe8a5 100644
--- a/lisp/mail/smtpmail.el
+++ b/lisp/mail/smtpmail.el
@@ -354,7 +354,8 @@ for `smtpmail-try-auth-method'.")
 		  (when (setq result
 			      (smtpmail-via-smtp
 			       smtpmail-recipient-address-list tembuf))
-		    (error "Sending failed: %s" result))
+		    (error "Sending failed: %s"
+                           (smtpmail--sanitize-error-message result)))
 		(error "Sending failed; no recipients"))
 	    (let* ((file-data
 		    (expand-file-name
@@ -437,13 +438,18 @@ for `smtpmail-try-auth-method'.")
                 (when (setq result (smtpmail-via-smtp
 				    smtpmail-recipient-address-list
 				    (current-buffer)))
-		  (error "Sending failed: %s" result))
+		  (error "Sending failed: %s"
+                         (smtpmail--sanitize-error-message result)))
               (error "Sending failed; no recipients"))))
 	(delete-file file-data)
 	(delete-file file-elisp)
 	(delete-region (point-at-bol) (point-at-bol 2)))
       (write-region (point-min) (point-max) qfile))))
 
+(defun smtpmail--sanitize-error-message (string)
+  "Try to remove passwords and the like from SMTP error messages."
+  (replace-regexp-in-string "\\bAUTH\\b.*" "AUTH" string))
+
 (defun smtpmail-fqdn ()
   (if smtpmail-local-domain
       (concat (system-name) "." smtpmail-local-domain)