Start/notes.ini Parameters/RouterDisableNDR

RouterDisableNDR

🛠️
Parameter: RouterDisableNDR
Short description: Suppresses the sending of Non-Delivery Reports (NDRs) by the router – effective against backscatter spam.

Profile

Parameter
RouterDisableNDR
Category
Mail / Router
Component
Server
Available since
R7
Supported versions
9.0.1, 10.0, 11.0, 12.0, 14.0, 14.5
GUI equivalent
Configuration document (Router/SMTP → Restrictions and Controls)
Possible values
0 = NDRs are sent (default), 1 = no NDRs

Description

With RouterDisableNDR=1, the router is told no longer to send Non-Delivery Reports to the senders of undeliverable mail. Background: spam is very often sent with forged sender addresses; an NDR sent to the forged address lands at an uninvolved third party as so-called backscatter spam.
In modern setups with an MX gateway / anti-spam, inbound mail is already rejected at the edge (5xx directly in the SMTP dialog), so Domino itself rarely has to issue NDRs anymore.

Example configuration

RouterDisableNDR=1

Notes & pitfalls

  • Legitimate senders also no longer receive feedback – communicate the impact before enabling.
  • Recommendation: reject inbound spam at the mail gateway rather than first at the Domino router.
  • For internal mail problems, there will be no NDR – the sender will not learn about the delivery failure.
  • The Configuration document offers more fine-grained options (selective NDR suppression).
  • The change only takes effect after a router restart (restart task router).