Dkimignore, dkimpreserve, dkimremove Channel Options

Source channel handling of DKIM-Signature: header fields
DKIM-Signature: header fields may require special handling, or their presence may indicate the need for special handling. The,  , and   source channel options provide various capabilities in this area.

The  source channel option instructs the MTA to take no special action in regards to DKIM-Signature: header fields. This option is the default.

The behavior of the  source channel option depends on whether the    and   MTA options are set. If neither of these options are set, the presence of any DKIM-Signature: header field in the message puts the MTA in  " " mode, where no header rewriting will be performed.

If either of the  or   MTA options is set, every DKIM-Signature: header field that is present will be parsed and the domain value specified by the " " will be extracted. Each extracted domain is first compared against the space-separated list of domains specified by the   MTA option. If a match is found no action is taken and processing continues with the next DKIM-Signature: field. If no match is found the domain is next checked against the space-separated list of domains specified by the    MTA option. If a match is found there the MTA is placed in " " mode and scanning is terminated.

The behavior of the  source channel option depends on whether the    and   MTA options are set. If neither of these options are set, all DKIM-Signature: fields are unconditionally removed from the message.

If either of the   or   MTA options is set, every  DKIM-Signature: header field that is present will be parsed and the domain value specified by the " " will be extracted. Each extracted domain is first compared against the space-separated list of domains specified by the  MTA option. If a match is found no action is taken and processing continues with the next DKIM-Signature: field. If no match is found the domain is next checked against the space-separated list of domains specified by the   MTA option. If a match is found there the corresponding DKIM-Signature: field is removed from the message.

See also the analogous destination channel options, introduced in 8.0.

See also:
 * destinationdkimignore Option
 * passthrough Option
 * dkim_ignore_domains MTA Option
 * dkim_preserve_domains MTA Option
 * dkim_remove_domains MTA Option
 * DKIM MTA options
 * DKIM channel options
 * Channel options