Parameter:
Router_MaxTransfer_AttemptsShort description: Maximum number of router delivery attempts before a message is marked as permanently undeliverable and returned via NDR.
Profile
Parameter | Router_MaxTransfer_Attempts |
Category | Mail / Router |
Component | Server |
Available since | 10.0 |
Supported versions | 10.0, 11.0, 12.0, 14.0, 14.5, 14.5.1 |
GUI equivalent | Configuration document (Router/SMTP → Restrictions and Controls → Transfer Controls) |
Possible values | Integer (default 25; typically 5–50) |
Description
When the router cannot deliver a mail (receiving server unreachable, DNS error, greylisting), it returns the message to
mail.box and retries after a wait cycle. Router_MaxTransfer_Attempts defines after how many attempts it gives up and generates an NDR (Non-Delivery Report).Lower values = faster feedback to the sender; higher values = more tolerance for temporary issues.
Example configuration
Router_MaxTransfer_Attempts=10
Notes & pitfalls
- Control the wait time between attempts via Initial Transfer Retry Interval.
- Pairs with
Router_MailHoldOnFailure,Router_DSN_Delay_Threshold.
- For SMTP hubs facing the internet, higher values (>20) make sense – external recipients are often briefly unreachable.
- For internal hops with stable connections, lower values (5–10) are sufficient.
- The change takes effect after a router restart or via
tell router quit/load router.