Alternatechannel, alternateblocklimit, alternatelinelimit, alternaterecipientlimit Channel Options
Triggering alternate channel processing (
It is sometimes useful to force processing of messages meeting certain criteria to occur on a channel distinct from the one chosen by the MTA's alias expansion and rewriting process. The
alternatechannel channel option provides a means to specify such a channel while the
alternaterecipientlimit channel options specify the criteria for when the alternate channel should be used.
alternatechanneltakes the name of the alternate channel to use as an argument.
alternateblocklimit takes an unsigned integer as an argument; the alternate channel will be used if the computed block size of the message exceeds this value.
alternaterecipientlimit also takes an unsigned integer argument; the message will be queued to the alternate chanmel if the number of recipients queued to the current channel exceeds this value. Finally, the
alternatelinelimit channel option takes an unsigned integer argument; the alternate channel will be used if the computed number of lines in the message exceeds this value.
alternaterecipientlimit is a limit on envelope recipients for this message copy, on this channel; it has nothing to do with how many addresses may or may not be in the header; and envelope recipients on other channels are also irrelevant. However, the
alternaterecipientlimit check does get performed before any message copy split-up due to storage of recipients per file controls such as
single_sys channel option application.
Note that any
*MAIL_ACCESS mapping table probes will use the "original" destination channel name, not the alternate destination channel name, but a
CONVERSIONS mapping table probe will use the alternate destination channel name.
Note that the alternate channel selection process is neither iterative nor recursive: Once an alternate channel has been selected it will be used regardless of what the various alternate channel options on that channel say to do.