diff --git a/core/nginx/conf/nginx.conf b/core/nginx/conf/nginx.conf
index df598c94..f7d9f074 100644
--- a/core/nginx/conf/nginx.conf
+++ b/core/nginx/conf/nginx.conf
@@ -215,7 +215,7 @@ mail {
     {% endif %}
 
     # Advertise real capabilites of backends (postfix/dovecot)
-    smtp_capabilities PIPELINING SIZE {{ MESSAGE_SIZE_LIMIT }} ETRN ENHANCEDSTATUSCODES 8BITMIME DSN CHUNKING;
+    smtp_capabilities PIPELINING SIZE {{ MESSAGE_SIZE_LIMIT }} ETRN ENHANCEDSTATUSCODES 8BITMIME DSN;
     pop3_capabilities TOP UIDL RESP-CODES PIPELINING AUTH-RESP-CODE USER;
     imap_capabilities IMAP4 IMAP4rev1 UIDPLUS SASL-IR LOGIN-REFERRALS ID ENABLE IDLE LITERAL+;