diff --git a/cluster/prod/app/email/config/postfix/main.cf b/cluster/prod/app/email/config/postfix/main.cf
index 2d0b992..a83e5ec 100644
--- a/cluster/prod/app/email/config/postfix/main.cf
+++ b/cluster/prod/app/email/config/postfix/main.cf
@@ -90,6 +90,7 @@ slow_destination_concurrency_limit = 2
 #====
 # Transport configuration
 #====
+default_transport = smtp-ipv4
 transport_maps = hash:/etc/postfix/transport
 virtual_mailbox_domains = ldap:/etc/postfix/ldap-virtual-domains.cf
 virtual_mailbox_maps = ldap:/etc/postfix/ldap-account.cf