opensmtpd-filter-dkimsign

Library for writing opensmtpd filters

This filter adds a DKIM signature to emails sent through OpenSMTPd. The rsa and ed25519 signing algorithms are supported, as well as the simple and relaxed canonicalization algorithms. The filter can sign emails for several domains, selecting them according to the from-header, but can only use a single selector, managing multiple selectors must be done at the OpenSMTPd level. It depends on the libopensmtpd port. An example of a minimal configuration for signing outgoing emails for domain "example.com" and selector "_selector" would be: filter "dkimsign" proc-exec "filter-dkimsign -d example.com -s _selector \ -k /usr/local/etc/smtpd/dkim/private.key" user _smtpd group _smtpd And then you can apply that filter to the mail that needs to be signed: listen on lo0 filter dkimsign