diff --git a/mail-server/dovecot.nix b/mail-server/dovecot.nix
index 2f83a86..5ba9c26 100644
--- a/mail-server/dovecot.nix
+++ b/mail-server/dovecot.nix
@@ -278,6 +278,9 @@ in
         ];
         disable_plaintext_auth = true;
 
+        # hostname
+        hostname = cfg.fqdn;
+
         # backend services
         "service auth" = {
           "unix_listener auth" = {