opendkim is in community repo.
dmarc and dkim are now in broad use by the major internet mail
companies (google, yahoo, microsoft, etc). If a maintainer is willing,
it would makes sense to move opendmarc from AUR to community as well.
For those who may not know, while dkim cryptographically validates
the domain of the sender in email, dmarc takes the next step and
validates that the domain in the From: header matches the dkim domain.
It's simple but effective way to be comfortable that the sender domain
is who it claims to be.
Thanks.
gene