diff --git a/lisp/gnus/message.el b/lisp/gnus/message.el
index fdb296fc24c..b979e1c5044 100644
--- a/lisp/gnus/message.el
+++ b/lisp/gnus/message.el
@@ -4676,9 +4676,11 @@ that instead."
 	(message-send-mail-with-sendmail))
        ((equal (car method) "smtp")
 	(require 'smtpmail)
-	(let ((smtpmail-smtp-server (nth 1 method))
-	      (smtpmail-smtp-service (nth 2 method))
-	      (smtpmail-smtp-user (or (nth 3 method) smtpmail-smtp-user)))
+	(let* ((smtpmail-smtp-server (nth 1 method))
+	       (service (nth 2 method))
+	       (port (string-to-number service))
+	       (smtpmail-smtp-service (if (> port 0) port service))
+	       (smtpmail-smtp-user (or (nth 3 method) smtpmail-smtp-user)))
 	  (message-smtpmail-send-it)))
        (t
 	(error "Unknown method %s" method))))))