Repeated rewriting template

Repeated rewriting template, A%B
The special rewrite rule template format A%B is used for "meta-rules" that require additional rewriting after their  application. When an A%B pattern is encountered, A becomes the new username and B becomes the new host/domain specification, and then the  entire rewriting process is repeated on the resulting new address. All other rewrite rule formats cause the rewriting process to terminate  after the rule has been applied.

For example, the rule .removeable     $U%$H has the effect of removing all occurrences of the   domain from the ends of addresses.

Extreme care must be taken when using these repeating rules; careless use can create a "rules loop" that will hang the MTA in an  infinite loop. (The MTA will attempt to detect simple cases of such loops to abort out after 100 repetitions: but even so this is (a) inefficient use of the MTA computation time, and (b) not fail-safe, as more complex loops may not be detectedable by the MTA.)  For this reason meta-rules should only be used when  absolutely necessary. Be sure to test them with the command.

See also:
 * Rewrite rule template formats