diff --git a/init.org b/init.org
index 550786b..db037b0 100644
--- a/init.org
+++ b/init.org
@@ -2979,7 +2979,11 @@ PR ideas
   (setq user-mail-address  "contrapunctus@disroot.org"
         user-full-name     "contrapunctus"
         smtpmail-smtp-user "contrapunctus"
-        auth-source-debug  'trivia))
+        auth-source-debug  'trivia
+        ;; Use system hostname to prevent "Sending failed: ...: Helo
+        ;; command rejected: need fully-qualified hostname" error when
+        ;; sending mail
+        mail-host-address  nil))
 #+END_SRC
 
 *** wanderlust                                                   :disabled: