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19.7 Rule Sets 1 and 2Rule sets 1 and 2 handle sender and recipient addresses, respectively. Rule set 1 is called before the S= delivery agent's rule set is called. Rule set 2 is called before the R= delivery agent's rule set is called. Neither is used (by default) in modern configuration files. 19.7.1 Rule Set 1Rule set 1 is intended to process all sender addresses. It is rarely used but can find application at sites where all outgoing mail should appear to come from a central mail server. Rules to handle this host-hiding might look like this: R $* <@ $=w> $* $@ $1 <@ $M> $3 user@localhost => user@ourdomain In the LHS the $=w matches any name from a list of names by which the local host is known. In the RHS the $M contains the name of the mail server. If the mail is not from the local host, it is unchanged. Other uses for rule set 1 might include the following:
Needless to say, great care should be exercised in adding schemes such as these to your configuration file. See LOCAL_RULE_1 (Section 4.3.3.3) for a way to add rules to rule set 1. 19.7.2 Rule Set 2All recipient addresses are rewritten by rule set 2 and the R= of delivery agents. But in almost all configuration files, rule set 2 is unused because no processing is needed: # Recipient processing: none needed S2 But note that rule set 2 can be used to debug rules.[6] Consider the following rule in rule set 2 (that requires V8.9 and above sendmail to work):
R $# $+ $: $+ $:$2 Strip delivery agent and host when debugging Recall that the parse rule set 0 returns a triple. When testing an address, rule set 2 can be called following the parse rule set 0 to simulate the rewriting of the user portion of the parse rule set 0. Here the LHS matches only a triple, so normal recipient addresses are unaffected. The user part that is returned by the RHS can then be used to test individual R= rules of delivery agents. (Another technique is to use the /try command in -bt rule-testing mode; see Section 8.5.6.) See LOCAL_RULE_2 (Section 4.3.3.3) for a way to add rules to rule set 2. |
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