Start/notes.ini Parameters/MailMaxThreads

MailMaxThreads

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Parameter: MailMaxThreads
Short description: Maximum number of parallel router threads for delivery into local mail databases.

Profile

Parameter
MailMaxThreads
Category
Mail / Router
Component
Server
Available since
R6
Supported versions
9.0.1, 10.0, 11.0, 12.0, 14.0, 14.5
GUI equivalent
Configuration document (Router/SMTP → Restrictions and Controls → Transfer Controls)
Possible values
Integer, default 25; typically 25–50 on hub / mail servers

Description

The Domino router delivers mails into local mail databases (mail\xy.nsf) in parallel. MailMaxThreads defines how many of these delivery threads may run concurrently. On servers with high mail load (large distribution lists, many users), a higher value increases throughput, but also raises I/O and CPU load. On small or application-heavy servers, the default is sufficient.
Not to be confused with RouterMaxConcurrentTransfer, which controls parallel transfer threads to other servers.

Example configuration

MailMaxThreads=50

Notes & pitfalls

  • Values significantly above 50 are rarely useful – disk I/O or the indexer become the bottleneck.
  • Takes effect after a router restart (tell router quit / load router) or the next configuration reload.
  • Pairs with RouterMaxConcurrentTransfer (server-to-server transfer) and MAIL_LOG_TO_MISCEVENTS for diagnostics.
  • With very high values combined with large distribution lists, watch out for NSF locking (especially in a cluster).
  • Monitor performance impact via show stat Mail.* and show stat Router.*.