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12. Delivery Errors and Retrying > Timeout of Retry Data

Timeout of Retry Data

One problem with Exim’s use of a host-based rather than a message-based retrying scheme arises when a host is tried only infrequently. A common example is an MX secondary host for some domain. Suppose there is a period of network failure, such that both the primary and the secondary host for a domain are unreachable. Retry data for both of them is computed. When the network comes back, mail is delivered to the primary server, leaving the retry information for the secondary still set. It could be weeks or months before the secondary is tried again. If it then fails, Exim could be in danger of concluding that it had been down all that time.

To circumvent this problem, Exim timestamps the data that it writes to its retry hints database. When it consults the data during a delivery, it ignores any that is older than the value set in


  

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