Start/notes.ini Parameters/SMTPClientDebug

SMTPClientDebug

SMTPClientDebug enables capturing of outbound SMTP protocol conversations from the Domino mail router — i.e. the connections Domino itself opens to foreign SMTP servers when forwarding mail via SMTP.

Profile

Parameter
SMTPClientDebug
Component
Server (Router/SMTP client)
Category
Mail / Router (debug)
Available since
9.0.x (per KB0032184)
Default
0 (disabled)
Values
0 off, 1 on
Output destination
log.nsf → Miscellaneous Events section (no debug_outfile needed)
What is logged
SMTP commands and responses, not the message body

Description

When SMTPClientDebug=1 is set, the Domino router writes the high-level protocol dialog for every outbound SMTP connection. Captured items include:
  • TCP connection setup to the target MX,
  • HELO/EHLO handshake,
  • TLS/STARTTLS negotiation (success, rejection, cipher),
  • authentication steps (AUTH),
  • envelope commands MAIL FROM, RCPT TO, DATA
  • response codes from the remote side (e.g. 250, 354, 421, 554),
  • connection teardown (QUIT, sockets, timeouts).
The actual message body between DATA/. is not logged — for that, SMTPSaveImportErrors (inbound) or another trace mechanism may be applicable.

Difference from SMTPDebug/SMTPDebugIO

According to KB0032184, SMTPClientDebug is the only of the router SMTP debug flags that does not require debug_outfile. The capture lands automatically in log.nsf in the Miscellaneous Events section. For SMTPDebug and SMTPDebugIO, on the other hand, a debug_outfile=path/file.txt is mandatory.

Examples

Activation in notes.ini (takes effect after router/SMTP restart):
SMTPClientDebug=1
Dynamically at runtime via the server console:
set config SMTPClientDebug=1
tell router quit
load router
Deactivate — set back to 0 and reload the router:
set config SMTPClientDebug=0
tell router quit
load router

Notes

  • Outbound direction only – For inbound SMTP conversations, SMTPDebug (listener) or SMTPDebugIO (bytes/content) is responsible.
  • log.nsf grows – With heavy outbound mail traffic, many Miscellaneous Events are generated. Turn off again after troubleshooting.
  • Privacy – Even though message content is not captured, envelope addresses (MAIL FROM, RCPT TO) are personally identifiable and are logged.
  • TLS issues – Very useful for detecting STARTTLS errors or certificate mismatches against external SMTP recipients.

Sources (HCL Product Documentation)