diff --git a/nixbld-etc-nixos/configuration.nix b/nixbld-etc-nixos/configuration.nix
index df2cbca9..e61ece39 100644
--- a/nixbld-etc-nixos/configuration.nix
+++ b/nixbld-etc-nixos/configuration.nix
@@ -755,7 +755,8 @@ in
 
       mailer = {
         ENABLED = true;
-        SMTP_ADDR = "mail.m-labs.hk:587";
+        SMTP_ADDR = "mail.m-labs.hk";
+        SMTP_PORT = "587";
         FROM = "sysop@m-labs.hk";
         USER = "sysop@m-labs.hk";
       };