But in
almost all configuration files, rule set 2 is unused because no processing is needed:
# Recipient processing: none needed
S2
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19.9 Policy Rule Set Reference | 703
But note that rule set 2 can be used to debug rules.* 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 ?§8.5.6 on page 313.)
See LOCAL_RULE_2 (?§17.3.3.3 on page 596) for a way to add rules to rule set 2.
19.8 Pitfalls
??? Rules that hide hosts in a domain should be applied only to sender addresses.
Avoid the temptation to place such substitutions of hosts for domain names into
the canonify rule set 3. The canonify rule set 3 applies to all addresses and can
wrongly change a nonlocal address.
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