diff --git a/install/tpl/postfix_3-0.conf.master b/install/tpl/postfix_3-0.conf.master
index ce4fc920ed0c6fccd0b5fcc034d27a1f84490ed1..b0f831883e411d791c4dd99cea6991e9f15d6c0d 100644
--- a/install/tpl/postfix_3-0.conf.master
+++ b/install/tpl/postfix_3-0.conf.master
@@ -14,3 +14,6 @@
 # validate DANE
 smtp_dns_support_level = dnssec
 smtp_tls_security_level = dane
+
+# Disable SMTPUTF8 (until Dovecot supports it: https://git.ispconfig.org/ispconfig/ispconfig3/-/issues/6428)
+smtputf8_enable = no
\ No newline at end of file