Additional generic options for routers

The following additional generic options apply to all routers, in addition to the common generic options for both directors and routers which are described in chapter "Common generic options for directors and routers". Routers are concerned with addresses whose domains do not match something in `local_domains'.

pass_on_timeout (router) option

Option: pass_on_timeout
Type: boolean
Default: false

If a router times out during a host lookup, it normally causes deferral of the address. If `pass_on_timeout' is set, the address is instead passed on to the next router. This may be helpful for systems that are intermittently connected to the Internet.

There are occasional other temporary errors that can occur while doing DNS lookups. They are treated in the same way as a timeout, and this option applies to all of them.

self (router) option

Option: self
Type: string
Default: "freeze"

This option specifies what is to happen if routing a remote address ends up pointing at the local host, or at a host whose name matches the `hosts_treat_as_local' option. Normally this indicates either an error in Exim's configuration (for example, the domain should be listed as local), or an error in the DNS (for example, the MX shouldn't point at this host). The default action is to freeze the message. The following alternatives are provided for use in special cases:

• `defer'
  Delivery of the message is tried again later.
• `reroute: <domain>'
  The domain is changed to the given domain, and the address is passed back to be reprocessed by the directors and routers. No rewriting of headers takes place.
• `reroute: rewrite: <domain>'
  The domain is changed to the given domain, and the address is passed back to be reprocessed by the directors and routers. Any headers that contain the original domain are rewritten.
• `local'
  The address is passed to the directors, as if its domain were a local domain, even though it does not match anything in `local_domains'. This can be used to treat all domains whose lowest MX records point to the host as local domains. During directing (and any subsequent local deliveries) the variable `$self_hostname' is set to the name of the local host that the router encountered. This can be used to distinguish between different cases for hosts with multiple names.
• `fail_soft'
  The router fails, leaving the address to be passed to any following routers.
• `fail_hard'
  The router fails, and the address is not passed to any following routers. Consequently, delivery fails and an error report is generated.
• `send'
  The anomaly is ignored and the message is transmitted anyway. This setting should be used with extreme caution. It makes sense only in cases where the program that is listening on the SMTP port is not this version of Exim. That is, it must be some other MTA, or Exim with a different configuration file that handles the domain in another way.

When a router just rewrites, that is, does not set up IP addresses, the `self' option is not relevant.

Skipping routers

Some of the generic options can cause routers to be skipped in particular cases. They interact with each other in the following way:

If the domain and local part are not in agreement with `domains', `except_domains', `except_local_parts' and `local_parts' (when set), or if the `condition' option fails, or if `verify_only' is set but verification is not happening, then the router is skipped and the next one is tried. None of the other options are inspected.

Otherwise, if the `more' option is not set, no subsequent routers are ever called, in any circumstances. The current router is itself called unless

• Verification is happening and its `verify_sender' or `verify_recipient' option (as appropriate) is turned off, or
• The existence or non-existence of files listed in the `require_files' option is not as expected, or
• The sender of the message is not in agreement with `senders' and `except_senders'. This test is done after checking for file existence so that sender lists can contain references to files whose existence is tested.

The `unseen' option causes routing to continue when it would otherwise cease, the complementary action to `no_more', which causes it to cease when it would otherwise continue.

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