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5.2.1 Concatenations

It is important to understand that conditional expressions choose the first match. To illustrate this, lets suppose you wish to store all recipient emails from the envelope in the ‘X-Also-Delivered-To’ header. A naive way to do so is:

if command [rcpt to:] = "(.*)"
  add header [X-Also-Delivered-To] "\1"
fi

However, this will store only the very first RCPT TO value, so you will not achieve your goal.

To help you in this case, anubis offers a concatenation operator, whose effect is to concatenate the values of all requested keys prior to matching them against the regular expression. Syntactically, the concatenation operator is a string enclosed in parentheses, placed right after the key part of a condition. This string is used as a separator when concatenating values. For example:

if command [rcpt to:] (",") = "(.*)"
  add header [X-Also-Delivered-To] "\1"
fi

This fragment will first create a string containing all RCPT TO addresses, separated by commas, and then match it against the regular expression on the right hand side. Since this expression matches any string, the ‘\1’ will contain a comma-separated list of addresses.


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