Start/notes.ini Parameters/RouterMaxConcurrentTransfer

RouterMaxConcurrentTransfer

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Parameter: RouterMaxConcurrentTransfer
Short description: Maximum number of concurrent transfer threads the mail router opens to a single target server.

Profile

Parameter
RouterMaxConcurrentTransfer
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 1 (recommended 2–5 for high mail volumes)

Description

RouterMaxConcurrentTransfer controls how many transfer threads the mail router may open in parallel to the same target server. More threads = faster backlog clearing and higher throughput, but also more load on the target server and on the connections in between.
The setting in the Configuration document – if present – takes precedence; the notes.ini value acts as a fallback or as an override for servers without a Configuration document.

Example configuration

RouterMaxConcurrentTransfer=3

Notes & pitfalls

  • On individual mail servers, the default 1 is usually sufficient.
  • On hub / bridgehead servers and heavily used SMTP outbound servers, 3–5 threads are worthwhile.
  • Values > 5 often saturate the network / target server more than they help – monitor (Mail.Transfer.*).
  • Works together with MailMaxThreads (delivery into local mail files).
  • The change only takes effect after a router restart (restart task router).