Rules, norules Channel Options
Channel-specific rewrite rules (
rules channel option tells the MTA to enforce channel-specific rewrite rule checks, and can be placed on source channels and on destination channels. When placed on a source channel,
rules allows source channel-specific effects from
$M control sequences in a rewrite rule template to take effect when that source channel is enqueueing a message and rewriting addresses. When placed on a destination channel,
rules allows destination channel-specific effects from
$Q control sequences in a rewrite rule template to take effect for addresses in messages being enqueued to that destination channel.
rules is the default.
norules tells the MTA not to check. These two channel options are usually used for debugging and are rarely used in actual applications.